Vasectomy may be associated with a small increase in absolute risk of prostate cancer, the findings from a large cohort study in the United States suggest. A cohort of 49,405 men taking part in the Health Professionals Follow-Up Study, run by Harvard University, was followed up from 1986 to 2010. During this period 12,321 men (25%) had vasectomies. [With external links to the current evidence base]