Women have glandular tissue below the bladder and surrounding the urethra that appears to be homologous to the male prostate. This tissue (also called "female prostate" or Skene's glands) appears to the source of a viscous, white secretion, which exits from the urethra upon sexual stimulation in some women. Analysis of this secretion (also known as "female ejaculate"), and comparison with pre-coital urine from the same women, revealed that its composition was unlike urine and often contained components also found in male seminal fluid (minus the sperm). The female ejaculate had lower levels of creatinine, but had elevated levels of prostate specific antigen, prostatic acidic phosphatase, prostate specific acid phosphatase, and glucose. The functional importance of female ejaculate has yet to be fully elucidated. It is possible that retention of a prostatic tissue homolog and its glandular secretion in women is merely a vestige of development and differentiation from an embryonic, gender-neutral body plan. We hypothesize that female ejaculation has a unique function in producing a secretion into the urethra that provides protection from urinary tract infections (UTIs). We further predict that female ejaculate contains antimicrobial compounds including elements such as zinc. We also hypothesize that retention of prostatic tissue and an ability to ejaculate its glandular secretion were maintained in women because these traits provided an evolutionary advantage. Specifically: (1) women who could ejaculate antimicrobial secretions into the urethra were less likely to suffer UTIs (particularly coitus-induced UTIs), (2) women without UTIs were more likely to be receptive to coitus at a greater frequency, (3) women engaging in frequent coitus were more likely to become pregnant, and (4) women who became pregnant often were more likely to successfully reproduce the species.