The comorbidity between premature ejaculation (PE) and erectile dysfunction (ED) has not yet been clarified.To assess the comorbidity between PE and ED.Male members of a shopping club in Taiwan aged 20-60 years with stable sexual relationships were invited to complete an online questionnaire.Self-estimated intravaginal ejaculatory latency time (IELT), Premature Ejaculation Diagnostic Tool, Sexual Health Inventory for Men, Self-Esteem and Relationship, and Hospital Anxiety and Depression Scale results were used.A total of 937 participants with a mean age of 41.1 ± 10.2 years were enrolled. The prevalence rates of ED (Sexual Health Inventory for Men ≤ 21), PE (Premature Ejaculation Diagnostic Tool ≥11), and IELT ≤1 minute were 24.7%, 6.3%, and 6.4%, respectively. Prevalence of acquired PE and IELT ≤1 minute increased marginally with age. Participants with ED had a greater prevalence of PE than those without ED (19.5% vs 2.0%, P < .001), and participants with PE had a greater prevalence of ED than those without PE (76.3% vs 19.4%, P < .001). Compared with participants without PE, participants with PE had greater adjusted odds of ED (odds ratio [OR] = 12.7, 95% CI = 6.7-24.2). Relative to participants without ED, participants with ED had increased adjusted odds of PE (OR = 7.2, 95% CI = 3.5-14.6 with mild ED and OR = 36.7, 95% CI = 16.2-83.0 with ED severity greater than a mild degree). Poor sexual relationships and self-esteem, depression, and anxiety were reported more frequently in those with PE or ED, especially in those with both problems compared with those without PE and ED.This study confirmed a high prevalence of PE and ED coexistence, indicating a complicated relationship between the 2 conditions and the importance of screening for their co-occurrence in practice. Tsai W-K, Chiang P-K, Lu C-C, et al. The Comorbidity Between Premature Ejaculation and Erectile Dysfunction-A Cross-Sectional Internet Survey. Sex Med 2019;XX:XXX-XXX.