A total of 19 cocaine-dependent male inpatients received 60 mg of FEN or a placebo (double-blind). Data were compared with those obtained in a previous study of another serotonergic probe, the partial postsynaptic agonist meta-chlorophenylpiperazine (m- CPP). FEN significantly reduced cocaine craving and increased cortisol and prolactin when compared with the placebo. When the responses to the two drugs were compared, there were no differences in the cortisol and prolactin rises, but m-CPP was a more potent inhibitor of cocaine craving than FEN. These data suggest that 5-HT releasers/reuptake inhibitors and serotonergic agents with greater postsynaptic activity should be further examined. Future studies will require the use of different doses of m-CPP and FEN. Additional long-term studies are also needed to determine whether 5-HT postsynaptic agonists would be different from 5-HT releasers/reuptake inhibitors in their ability to decrease cocaine use. 1 table, 6 figures, and 24 references