Behavioral disturbances are a commonfeature of Alzheimer's disease (AD). Prior studies have demonstrated a significant reduction in agitation behaviors during short-term exposure to a dog on an Alzheimer's special care unit (SCU)for persons with AD. The purpose of this study was to determine the effect over time of a resident dog on problem behaviors of persons with AD in an SCU. A within-participants repeated-measures design was used for this study. The Nursing Home Behavior Problem Scale was used to document behaviors (on days and evenings) I week before and 4 weeks after placement of the dog. Participants on the day shift exhibited significantly fewer problem behaviors across the 4 weeks of the study (F[1, 80] = 7.69, p < .05). No significant change in behaviors occurred on the evening shift. Thefindings support the long-term therapeutic effects of dogs for persons residing in Alheimer's SCUs.