The rhythmic contractions of the prostate, perineal muscles and shaft of the penis occur initially at 0.8-second intervals, just as in women, and account for the spurting action of the semen during ejaculation. The intervals between contractions become longer and the intensity of the contractions tapers off after the first three or four contractions.

The semen does not actually appear until a few seconds after the point of ejaculatory inevitability because of the distance the seminal fluid has to travel through the urethra. During ejaculation, the internal sphincter of the urinary bladder is tightly sealed to make sure that the seminal fluid travels forward and to prevent any urine from mixing with the semen.

Male ejaculation and orgasm are not one and the same process, although in most men and under most circumstances the two occur simultaneously. Orgasm refers specifically to the sudden and rhythmic muscular contractions in the pelvic region that release accumulated sexual tension and result in an intensely pleasureable sensation.

Sometimes ejaculation occurs involuntarily and unbeknownst to the man during sleep. This is known as nocturnal emission or, in slang terms as a "wet dream" and is particularly common in adolescents and young men.