In this article, the authors examine the effect of lisuride on 22 patients with probable Alzheimer's disease (NINCDS/ADRDA criteria) in a randomized double-blind, placebo-controlled, parallel group design. Ten patients received lisuride and 12 patients received placebo. Lisuride was administered in a dose-finding phase of four weeks and an efficacy phase of eight weeks, with a maximum dose of 0.3 mg daily. Outcome measures included global clinical impression, general cognitive function, mood, verbal and visual memory, attention, and psychomotor function. Average decline in Mini-Mental State Examination score after 12 weeks treatment was less often statistically significant in lisuride treated patients than in patients receiving a placebo (p < 0.05). Patients treated with lisuride improved their average total score and short-delay cued recall score on the California Verbal Learning Test, a test of verbal memory, whereas placebo-treated patients showed worse performance compared with baseline. These differences approached statistical significance, with p = 0.06 and p = 0.05, respectively. No other differences between the treatment groups were evident. The authors failed to find a consistent effect of lisuride on symptoms of Alzheimer's disease. However, this study's sample size was relatively small, and larger studies are needed to ascertain the treatment effects of serotonergic antagonists on Alzheimer's disease.