To investigate the relationship between the fetal androgen exposure and lifelong premature ejaculation by using the ratio of the second (index)-to-fourth (ring) digits (2D:4D) which is the marker for higher prenatal androgen exposure. Totally 65 patients with lifelong premature ejaculation and 65 control cases without any ejaculatory complaints were enrolled in the study. A detailed medical history was obtained and self-estimated intravaginal ejaculatory latency times were recorded. Ejaculation function was evaluated by Premature Ejaculation Diagnostic Tool. The lengths of the second and fourth digits of both hands were measured and 2D:4Ds were calculated. The mean 2D:4D values were 0.964 +/- 0.024 vs. 0.978 +/- 0.032 (p=0.004) for the right hand and 0.966 +/- 0.023 vs. 0.979 +/- 0.032 (p=0.006) for the left hand in lifelong premature ejaculation and control groups, respectively. Significant correlations were observed between the digit ratios and self-estimated intravaginal ejaculatory latency time (r=0.258, p=0.003 for right hand; r=0.240, p=0.06 for left hand), and between the digit ratios and total Premature Ejaculation Diagnostic Tool scores (r=-0.263, p=0.003 for right hand; r=-0.238, p=0.06 for left hand). Individuals with lower digit ratios have higher risks of shorter intravaginal ejaculatory latency times. These results suggest that increased fetal androgen exposure may be a new risk factor for the development of lifelong premature ejaculation.