Introduction. Low testosterone levels (low T) increase the cardiovascular (CV) risk of men with erectile dysfunction (ED). T levels associated with a higher CV risk are unknown. Aim. To determine the prevalence of CV risk factors associated with low T as defined by European Guidelines and their contribution to low T, overall and at different ages. Methods. Multicenter, cross-sectional, observational study conducted in Spain among men with ED aged >= 18 years visiting Urology/Andrology offices for sexual dysfunction. Anthropometric, clinical, and laboratory data, including total T (TT) values, were collected for 1,278 men. Main Outcome Measures. Risk factors were assessed in men with TT= 12 nmol/L, and two-group comparisons were made. Bivariate and multivariate logistic regression analyses were performed to calculate odds ratios for low T after adjusting for possible confounding factors. Results. Mean age (standard deviation) was 58.0 (9.2) years. Age and prevalence of CV risk factors was similar in men with TT12 nmol/L. Low T was therefore considered as TT <= 12 nmol/L, with a prevalence of 33.3%. Obesity, hypertension, hyperlipidemia, and severe ED were the variables most strongly associated with low T: obesity in middle-aged men; hyperlipidemia, and hypertension in older men. Severe ED was a risk factor in both groups. Hypolipidemic therapy had the greater effect in young men. Multivariate analysis showed that severe ED and obesity were the strongest predictors of low T. Conclusion. T levels associated with increased CV risk could go as high as 12 nmol/L in men with ED, with distribution of risk factors showing differences according to age. Obesity and severe ED are the best predictors of low T-related CV risk.