A double-blind randomized controlled study was conducted in 42 hospitalized demented patients to evaluate the therapeutical effect of phosphatidylserine (BS-PS). Half of the patients received 3 X 100 mg of this product, and the other half a placebo of the same appearance. After a wash-out period, prescription lasted for six weeks. To evaluate the patients, two distinct rating scales were used: the Crichton Scale and an original one (Peri Scale) designed in our geriatric unit (see Appendix). A circle crossing test was added. Out of the 35 patients who completed the trial, 18 had received placebo and 17 BC-PS. The results indicated a trend toward improvement in the BC-PS treated patients and an analysis of covariance showed a significant (p less than 0.05) treatment effect on the Peri Scale. The results at the end of the treatment period were compared with those obtained three weeks later. Here again there was a statistically significant difference in the Peri Scale results, indicating that modifications are drug-related. The behavioral improvement shown in this study is in agreement with experimental studies on aged animals.