Larger penis size has been equated with a symbol of power, stamina, masculinity, and social status. Yet, there has been little research among men who have sex with men assessing the association between penis size and social-sexual health. Survey data from a diverse sample of 1,065 men who have sex with men were used to explore the association between perceived penis size and a variety of psychosocial outcomes. Seven percent of men felt their penis was "below average," 53.9% "average," and 35.5% "above average." Penis size was positively related to satisfaction with size and inversely related to lying about penis size (all ps < .01). Size was unrelated to condom use, frequency of sex partners, HIV status, or recent diagnoses of HBV, HCV, gonorrhea/Chlamydia/urinary tract infections, and syphilis. Men with above average penises were more likely to report HPV and HSV-2 (Fisher's exact p <or= .05). Men with below average penises were significantly more likely to identify as "bottoms" (anal receptive) and men with above average penises were significantly more likely to identify as "tops" (anal insertive). Finally, men with below average penises fared significantly worse than other men on three measures of psychosocial adjustment. Though most men felt their penis size was average, many fell outside this "norm." The disproportionate number of viral skin-to-skin STIs (HSV-2 and HPV) suggest size may play a role in condom slippage/breakage. Further, size played a significant role in sexual positioning and psychosocial adjustment. These data highlight the need to better understand the real individual-level consequences of living in a penis-centered society.