There are no conclusive data available on the incidence or prevalence of endometriosis, yet the notion persists that the frequency of cases has dramatically risen in western societies during the past 25 years. Race, familial predisposition, reproductive history, socioeconomic status, personality type and a historical drop in age at menarche have been posited as risk factors for the complex and as-yet-unclear epidemiology of this disorder. The epidemiology of endometriosis is constrained by the difficulty of the diagnosis. Several analytic concepts from epidemiology, however, could be profitably used to further our knowledge of endometriosis. Included are the case-control study, survival and life-table analyses and correlations of psychologic traits with susceptibility to development of the disease. Though none of these techniques is original or without potential for bias, they may be underutilized in solving the conundrum of endometriosis.