This article aims to provide a systematic review of estimates and methodology of studies quantifying the costs of endometriosis. Included studies were cost-of-illness analyses quantifying the economic impact of endometriosis and cost analyses calculating diagnostic and treatment costs of endometriosis. Annual healthcare costs and costs of productivity loss associated with endometriosis have been estimated at $2801 and $1023 per patient, respectively. Extrapolating these findings to the US population, this study calculated that annual costs of endometriosis attained $22 billion in 2002 assuming a 10% prevalence rate among women of reproductive age. These costs are considerably higher than those related to Crohn's disease or to migraine. To date, it is not possible to determine whether a medical approach is less expensive than a surgical approach to treating endometriosis in patients presenting with chronic pelvic pain. Evidence of endometriosis costs in infertile patients is largely lacking. Cost estimates were biased due to the absence of a control group of patients without endometriosis, inadequate consideration of endometriosis recurrence and restricted scope of costs. There is a need for more and better-designed studies that carry out longitudinal analyses of patients until the cessation of their symptoms or that model the chronic nature of endometriosis.