Montessori materials were used in two adult day-care centers to slow cognitive decline in adults with Alzheimer'S disease. Using a within-subject design, participants in one adult day care received three months of the Montessori materials, then standard intervention later. Participants were administered a battery of cognitive measures at baseline, three months, and six months. Favorable scores for the Montessori condition were significant with the subscales of the Ordinal Scale of Psychological Development-Modified (total, object permanence, means-ends), Dementia Rating Scale (total, attention, concept, memory), Parachek Geriatric Behavior Rating Scale (social behavior), and the Wechsler Memory Scale (digit forward). Montessori materials appeared instrumental in positively influencing basic cognitive abilities of attention, object permanence, and social behavior. © 2003, Informa UK Ltd All rights reserved: reproduction in whole or part not permitted. All rights reserved.