Progressive dementias, such as Alzheimer's disease, account for approximately 50 percent of nursing home admissions in the US. As the national population ages, the number is increasing. Special care units (SCU) have evolved as one way to meet the needs of these patients. They are specially designed for the cognitively impaired, staff is specially trained, and activities are individualized. The present study was designed to identify factors contributing to the quality of care of demented patients in nursing homes. Sixty-three nursing home units, including both SCUs and non-SCUs, were observed and data was collected on the type and quality of care given, staff and administrative attitudes, overall environment, and the patient population. Ratings were then made and the authors classified the units into one of eight types: ideal, uncultivated, heart of gold, rotten at the core, institutional, limited, conventional, and execrable. The 'ideal' setting had a therapeutic rather than maintenance philosophy of care, an administration knowledgeable in dementia, a staff highly experienced in caring for memory-impaired patients, and an overall concern for staff and patients. Physical maintenance of the unit was important, as was its layout; patients had privacy and rooms were personalized. The first three types of units comprised 22 percent of the 63 units surveyed; 21 percent fell into the execrable, rotten at the core, or conventional categories. No SCUs fell into the two worst categories, and no non-SCUs fell into the two best. It is not clear why this is true, but it is possible that SCUs receive better funding and can therefore provide better overall care, or that differences in admission policies of the two types of units have an effect. The results show that SCUs can provide high-quality care for demented patients and that all SCUs are not equally able to do this. Consumers may use the types of units presented in this article as a general guideline in choosing nursing home care for a demented adult. (Consumer Summary produced by Reliance Medical Information, Inc.)