One hundred and fifty years ago Jonathan Hutchinson published the first data suggesting that male circumcision may be protective against syphilis. He found that among men consulting with a venereal disease circumcised (Jewish) men were less likely to suffer from syphilis than uncircumcised men.¹ About 20 years later Ephraim Epstein, a physician practising in the United States, pointed out that the association between syphilis and male circumcision may be confounded by sexual behaviour—long before “confounding” was used in the epidemiological sense of the word.² He phrased his concerns as follows: “In common with others, once I believed that circumcision affords a protection against venereal diseases, but my practice in Vienna, and in this country since 1862 persuaded me fully to the contrary. The apparent immunity which Jews of Russia and European Turkey seem to enjoy from venereal diseases arises from their greater chastity and the practice of early marriage.” More than a century later the effect of male circumcision on the risk …