Ten healthy young male volunteers (mean age 22 ± 3.7 years, range 19–31 years) spent three nights in our sleep laboratory for polysomnography (PSG). The first was the adaptation night and the second was the baseline night. On the third night the subjects received risperidone (1 mg tablet) 30 min before the PSG recording. Following risperidone administration, we observed a significant increase in the percentage of stage 2 sleep to sleep period time (SPT) and a significant decrease in the percentage of rapid eye movement (REM) sleep to SPT. This change of the stage 2 sleep was obtained in the first and second period of sleep. Moreover, we demonstrated that risperidone decreased stage 1 sleep in the first period of sleep. Risperidone treatment might improve the quality of sleep in schizophrenia.