SYNOPSISHeadache frequency and index in migraine patients both on and off oral contraceptives were observed.Twenty patients received an oral contraceptive for two months while another twenty patients did not. After two months the second group received the oral contraceptive, and the first did not. Increased frequency of headaches, and headache index most prominent in cases of moderate severity, occurred while the patients were on the pill. Three distinct groups of patients were identified. One group improved while on the pill; a second group had headaches and a third group showed no influence of oral contraceptives on headache.