Administration of 50 mg trazodone, an antidepressant drug, in a single oral dose to 10 normal subjects of both sexes, aged 24--41, resulted in a significant (p less than 0.01) decrease of serum prolactin (PRL) values. The mean serum PRL levels were 8.9 +/- 2.2 ng/ml in basal conditions and 4.5 +/- 1.7 ng/ml 180 min after trazodone. Pretreatment with trazodone does not modify TRH-induced PRL release.