In a 12-week double-blind study, piracetam at two dose levels (2.4 and 4.8g/day) was compared to placebo in the treatment of 60 elderly psychiatric patients with mild diffuse cerebral impairment, but no signs of focal brain lesion. The psychiatric illness, schizophrenia or affective disorder, of patients selected was in remission at the time of the study. Monthly evaluations by the nurse revealed that piracetam improved overall functioning, particularly alertness, socialization, and cooperation, relative to the control group. Patients treated with 2.4g/day piracetam also showed significant improvement in scores for the full IQ and the memory quotient on the Wechsler Adult Intelligence and Memory Scales; greater response was seen in those with lower initial scores. Piracetam at 4.8g/day had a more rapid onset of action on behavioral variables than 2.4g/day, but its therapeutic effect tended to diminish at 12 weeks, possibly as the result of overstimulation. Piracetam did not appear to interfere with concomitant psychotropic maintenance medication or affect the psychiatric illness itself.