Twenty-three premature ejaculators (PEs) and 11 control subjects were administered 25 mg of clomipramine in a double-blind, placebo-controlled, crossover design study. During 2-week trials, subjects took either the drug or the placebo 4 to 6 hours prior to sexual activity. Daily diary data revealed that, for both groups, orgasmic latency was significantly increased when taking the clomipramine. For the PEs, the average increase in orgasmic latency during intercourse was from less than 1 minute to more than 3.5 minutes. Subjects also participated in two laboratory sessions while on the drug and placebo. During these lab sessions they were exposed to erotic videos with and without the addition of vibrotactile stimulation to the penis. Results from the laboratory data support those from the diaries. Specifically, PEs were significantly less likely to reach orgasm during the lab sessions while on the clomipramine than while on the placebo. Further, they reported a significantly greater sense of control over their orgasm while on the drug. The results of this study, along with previous research, strongly support the value of low doses of clomipramine in the treatment of premature ejaculation, specifically when taken on an as-needed basis as little as 4 hours prior to sexual activity. It is important to note, however, that the beneficial effects of the drug were not uniform across clinical subjects. In this study, those PEs with the shortest orgasmic latencies while on the placebo were the least likely to substantially improve while on the drug. Additional research is necessary to determine whether changes in the timing and dosage of the clomipramine administration can extend the benefits of the drug to those with the shortest latencies.