Drug toxicity testing is required by the U.S. Food and Drug Administration in bitches of beagle dogs for 7 years and in female rhesus monkeys for 10 years at 25-50 times the human dosage. Progesterone, medroxyprogesterone acetate, megesterol acetate, chlormadinone acetate, chloroethynl norethisterone and chloroethynyl norgestrel are some compounds which have induced tumors in beagle dogs. However, the endocrinology of the beagles is unlike that of a woman and binding affinity of synthetic progestogens to breast cytoplasmic progesterone receptors of the beagle and women have striking differences. Some progestogen compounds which do not produce neoplasia in dogs because of too low a dose are most potent in women. Both the WHO and the Committee on Safety of Medicines concluded that progestogen-induced breast tumors in beagles are unhelpful in predicting possible breast cancer in women who use oral contraceptives.