This Letter to the Editor reports on 2 tests of 8 psychiatric suicide-attempt patients & 8 normal controls using a placebo & 0.25 mg/kg of the serotonin (5-HT) agonist, m-chlorophenyl-piperazine (MCPP). The study found similar MCPP-induced cortisol, prolactin, & behavioral responses in suicide attempters & healthy controls, suggesting that 5-HT receptor sensitivity in suicide attempters is not different from that of healthy controls. Results contrast with previous challenge studies.