Cambendazole paste 31% w/w, at 20 and 40 mg/kg, was tested in a series of field trials involving 237 horses of various ages, sex and pregnancy status. No drug-related sequelae were observed except for a mild anorexia in 10 thoroughbreds in training and on concentrate feed. Forty-nine thoroughbred mares, more than three months pregnant, showed no drug-related sequelae to themselves or their foals. Of 10 dosed at 80 or 160 mg/kg, one (80 mg/kg) showed elevated temperature at % hours after dosing.