OBJECTIVES: Little is known about the effect of obesity as quantified by the body mass index on the serum levels of sex hormones, antisperm antibodies, and postoperative fertility of men undergoing vasectomy reversal. The aim of the present study was to investigate the effect of obesity on sex hormone levels, the presence of antisperm antibodies, and fertility after vasectomy reversal. METHODS: We identified 500 patients with complete clinical and laboratory data who had undergone vasectomy reversal by a single surgeon. Data on postoperative vas patency and pregnancy were available for 315 and 334 patients, respectively. RESULTS: Postoperative vas patency was observed in 93.2%, 91.9%, and 93.3% of normal weight, overweight, and obese patients, respectively (P = .931). Pregnancy was achieved by the partners of 63.9%, 60.2%, and 55.6% of the normal weight, overweight, and obese patients, respectively (P = .672). An increased body mass index was associated with lower serum testosterone levels (P < .001). Significant associations were found between both patient age (P = .007) the and presence of IgA antisperm antibodies (P = .006) with the body mass index. In the logistic regression analyses, the age of the female partner was the only independent predictor of postoperative pregnancy (P = .039). CONCLUSIONS: Our results have highlighted that no specific testing before vasectomy reversal can aid in predicting the fertility outcome and that patients should be counseled that the age of their female partner will have an effect on their likelihood of conceiving after vasectomy reversal. In overweight and obese patients, the clinical signs of hypogonadism should be examined and the serum testosterone level should be investigated. © 2010 Elsevier Inc.