It is an aging baby boomer’s nightmare.

You visit your mother who lives a thousand miles away and find her home - usually neat as a pin - is a mess. Everything in the home is covered in a layer of dust, and the sink is piled high with dirty dishes. Plus, she looks like she’s been losing weight.

You panic and think, "She can’t live on her own anymore." You recall reading or hearing about something called "assisted living" residences. Aren’t they supposed to be good places for the elderly?

Indeed, the assisted-living concept is the hot new thing in senior residences, with dozens of new facilities opening every month across the country, each with its own glossy marketing brochures promising to take good care your loved ones.

Before getting too taken in by the brochures, however, here are some basics that will help your family make a wise decision when it comes to choosing a residential facility.

To begin with, assisted living has no formal legal definition. While nursing homes are closely regulated because they receive lots of federal and state financial assistance, the assisted-living industry doesn’t even have a single name to describe what it does.

Assisted-living facilities go by many names, including residential care facilities, adult congregate living facilities, personal care homes, catered living facilities, retirement homes, homes for adults, or community residences, according to the Assisted Living Federation of America or ALFA. The industry trade group estimates that 1 million people are living in more than 20,000 communities. The average resident is usually a woman in her 80s, ALFA reports.

Most often, as assisted-living unit is composed of individual apartments, with a common dining room in the building where the residents can get at least one meal a day. The level of "assistance" at assisted-living facilities varies tremendously, and you need to make sure the details of care and service are spelled out in any contract you sign.

Some residents might need only housekeeping services, such laundry and apartment cleaning. Others might need a reminder twice a day as to take their medications. And others might need someone to come in each morning to help a resident bathe and dress.

Assisted living is a sort of middle ground of care: more help than is available in an ordinary retirement community, but far less than the medical treatment and hands-on care common in a nursing home.

It’s a good idea to visit at least three places before you select one, so you have something to compare. Try not to be too impressed by the beautiful flowers in the lobby, the comfortable and cozy look of the reading room, or the reassuring words of a charming marketing director. If something your mother, father or spouse might need is not in the contract, you cannot count on getting it.

Rona Barelstoen, a geriatric case manager with a Fort Lauderdale, Fla., company that operates facilities for seniors, advises families to make at least two trips to a facility they are considering. "Go the first time and get the official tour," she says, "but then come back unannounced the second time. Look at the common areas and the dining room. Talk to the residents, talk to the staff members. See how they interact with each other."

Study the facility’s promotional materials carefully. Do they give only vague descriptions of the services provided? An example might be a description like this: "assistance with activities of daily living provided." If that’s the case, seek out more information, advises AARP, formerly the American Assn. of Retired Persons.

In a booklet titled "Navigating Your Way to a quality Assisted Living Facility," AARP tells consumers to get these questions answered:

• Does the company’s contract clearly spell out which daily activities residents are assisted with? For example, do they include personal grooming and, if so, does that mean help with shaving and brushing teeth and hair?
• Is assistance available around-the-clock or only during certain hours? Who provides the assistance and how many staff people are on duty?
• Must residents bathe at certain times of the day? How often is bathing assistance available?
• What assistance is given to people who are incontinent?

AARP’s Elinor Ginzler advises people not to sign a contract while visiting a facility. "Take the contract with you and show it to the family attorney before you sign it," says Ginzler, the AARP’s manager of long-term care and independent living. The only legally binding promises of service by the assisted-living facility and its staff are the ones in the contract.

These are huge differences in the potential cost. The industry says charges can range from $15 a day to $200 a day. There are lots of variables: Some states and cities have higher living costs, the size of the apartment makes a difference in the cost and most important, the services provided will vary significantly. If someone needs help bathing every day, that is a separate service with its own bill.

All these decisions should involve the participation and consent of the person who will live in the assisted-living apartment. The worst thing would be to take your mother from her home against her will. The loss of familiar surroundings can have a devastating emotional effect, the experts warn. That is why it is a good idea for families to have this discussion when Mom is still healthy, but beginning to slow down, and before any accident or illness forces a desperate search for a facility.

The General Accounting Office, the investigative arm of Congress, issued a report in 1999 that warned about consumer confusion and uncertainty in assisted-living facilities in four states. "Many facilities did not provide prospective residents with written information on such key issues as the amount of assistance they could expect to receive with medications, the circumstances under which the cost of services might change, or when they could be required to leave if their health changes." Moreover, GAO investigators "identified numerous examples of vague misleading or even contradictory information" in the written materials that were provided to the public.

There are other general sources of help with assisted-living issues. Long before Mom goes to the hospital but when you want some objective discussion of her needs, you can call a geriatric case manager. The manager will visit Mom at home, interview her about her life and its problems, check the house for possible safety hazards, confer with other family members and make recommendations. Maybe Mom needs someone to come in two or three times a week to help with cooking, cleaning and bathing. Or maybe she does indeed need to move to a more protected environment. A review by a geriatric case manager may cost from $400 to $700. The National Assn. of Geriatric Care Managers has more than 900 members. A nation-wide directory is available for $15 by calling (520) 881-8008. The organization is located at 1604 N. Country Club Road, Tucson, AZ 85716. Information is available for free on the Web site www.caremanager.org.

Information on assisted living is available from the Assisted Living Federation of America by calling (703) 691-8100. The group’s Web site is at www.alfa.org. A smaller group, which represents only the nonprofit segment of the business, is the American Assn. of Homes and Service for the Aging, or AAHSA. Its Web site is www.aahsa.org. Or you can call (202) 783-2242 for information.

Another group offering advice to potential residents and family members is the Consumer Consortium on Assisted Living. The Web site is www.ccal.org, and the phone is (703) 533-8121.