A syndrome associated with vaginal discharge, endometritis and reproductive inefficiency in the served sow is described. In some herds pregnancy failures exceeded 15 per cent with increased returns to service and sows not in pig. Predisposing factors included the age of the herd and the hygiene and management practices from weaning to service and during the 21 days after service. No one organism was implicated but venereal transmission was considered possible. One hundred and ten breeding herds were surveyed and in 26 of these control measures were necessary. These included antibacterial therapy of the prepuce of the boar and medication of the sow from weaning until 21 days after service. Such treatment together with management changes resolved the problem in 22 of the herds. The syndrome reappeared in four out of seven herds where treatment of the boar was not continued.