The purpose of this multicenter, randomized, double-blind, placebo-controlled parallel-group comparative study was to prove the efficacy and tolerance of sulpiride (150-300 mg) against placebo in mild to moderate depressive syndrome. The primary criterion of efficacy was the course of the HAMD total score from day 1 to day 42, compared between the two treatment groups. The duration of the treatment was six weeks, preceded by a one-week placebo run-in phase. The HAMD, CGI and KUSTA scores were determined, the tolerance assessed, and the laboratory parameters and serum prolactin levels determined before, during and at the end of the trial. 177 outpatients aged from 18 to 70 years with mild to moderate depressive syndrome (ICD-10: F32.0, F32.1, F33.0, F33.1) and a score of 18-27 points on the 21-item HAMD scale were randomized, 171 of whom (sulpiride: n=83; placebo: n=88) were included in the intention-to-treat analysis. All the baseline data recorded for the two groups displayed comparable values. The decrease of the HAMD score between day 1 and day 42 yielded a difference of 2.5 points in favour of the sulpiride group. This difference is statistically significant (p = 0.0007). The evaluations of the cases treated for at least 14 days or for 42 days (per protocol) showed consistent values. The analysis of the CGI values showed similarly distinct and clinically relevant differences for sulpiride in comparison with placebo. The evaluation of the KUSTA scores yielded mostly comparable values for the two groups. Adverse events occurred with about the same type and frequency in both groups, with severe adverse events occurring only in two placebo patients. The laboratory parameters revealed no significant differences between the treatment groups, with the exception of prolactin which moderately exceeded the range of normal in 50% of the patients treated with sulpiride. This trial proved that sulpiride is effective and well-tolerated when given in a mean dose of 181 mg per day for mild and moderate depression.