We examined chronic pelvic pain definitions used in published research, because the definition has direct implications for investigating causation and evaluating treatment. MEDLINE was searched for published articles in an Abridged Index Medicus journal from 1966 to 2001, restricted to humans, females, and English language. "Chronic pelvic pain" was used as a keyword. We reviewed 101 abstracts of publications of chronic pelvic pain. Forty-three articles met the criteria of human, female, English language, chronic pelvic pain, and use of an experimental, cohort, case-control, or cross-sectional study design. The following were not explicitly specified in the chronic pelvic pain definitions in these articles: duration of pain in 44%, restriction by pathology in 74%, location of pain in 93%, restriction by comorbidity in 95%, and additional inclusion/exclusion criteria in 65%. We conclude that an explicit chronic pelvic pain definition is not used for research of this population. The use of a poor operational chronic pelvic pain research definition reduces the ability to investigate causation and improve treatment of this condition.