The rationale for the diagnosis of Pelvic Inflammatory Disease (PID) was studied among hospitalized patients at the Department of Gynaecology, Regional Hospital of Trondheim, Trondheim. From 1 January 1991 to 31 December 1993, 153 patients were discharged with a diagnosis of Pelvic Inflammatory Disease. In retrospect, the diagnoses were reconsidered applying strict criteria. All 26 patients (17%) who had a diagnosis verified by laparoscopy were classified as suffering from a "true" diagnosis, 83 (54%) patients were reconsidered as suffering from a "more likely" and 44 (29% as suffering from a "less likely" diagnosis of Pelvic Inflammatory Disease. Women who had a laparoscopy verified diagnosis of Pelvic Inflammatory Disease, had higher ESR (erythrocyte sedimentation rate), C-reactive protein and temperature when compared with women reclassified as "less likely" suffering from Pelvic Inflammatory Disease. Only 72% of the patients had microbiological sampling from the cervix. In order to increase diagnostic precision we argue for minimum criteria and a systematic clinical examination, including vaginal ultrasound, when diagnosing Pelvic Inflammatory Disease. We recommend more diagnostic use of laparoscopy especially among women with mild symptoms and few objective signs.