The strikingly higher prevalence of migraine in females compared with males is one of the hallmarks of migraine. A large global body of evidence exists on the sex differences in the prevalence of migraine with female to male ratios ranging from 2:1 to 3:1 and peaking in midlife. Some data are available on sex differences in associated symptoms, headache-related disability and impairment, and healthcare resource utilization in migraine. Few data are available on corresponding sex differences in probable migraine (PM) and other severe headache (ie, nonmigraine-spectrum severe headache). Gaining a clear understanding of sex differences in a range of severe headache disorders may help differentiate the range of headache types. Herein, we compare sexes on prevalence and a range of clinical variables for migraine, PM, and other severe headache in a large sample from the US population.