Premature ejaculation (PE) is a form of male sexual dysfunction. An objective measurement of PE in clinical studies is the intravaginal ejaculatory latency time (IELT). This is a multicenter, placebo-controlled, double-blind, randomized, parallel-group study in men with PE. The study will consist 3 phases: pre-randomization phase (a screening visit and a 4-week baseline period); 24-week double-blind treatment phase during which patients will receive dapoxetine or placebo for use on an "as-needed" basis; and, 1-week double-blind withdrawal phase (dapoxetine or placebo) with a post-study telephone contact approximately 2 weeks after the end of treatment. The total duration of the study is approximately 31 weeks. Assessments of effectiveness include the average intravaginal ejaculatory latency time, as measured by stopwatch during sexual intercourse, during the treatment period; control over ejaculation, satisfaction with sexual intercourse, and severity of symptoms, based on questions asked at monthly intervals through the treatment phase. Safety assessments include the incidence, severity, and type of adverse events throughout treatment and follow up (Week 27), as well as laboratory tests and questionnaires to monitor possible changes in mood, anxiety, motor responses, and sexual function at specified times during the study. The study hypothesis is that treatment for 24 weeks with dapoxetine prolongs intravaginal ejaculatory latency time, compared with placebo, in men with PE. Oral tablets of dapoxetine (30 milligrams[mg] or 60mg) or placebo taken as needed during 24 weeks of treatment. No more than 1 dose within a 24-hour period.