OBJECTIVE: To assess the value of endometrial thickness measurement as a test for endometrial cancer in postmenopausal women with vaginal bleeding (symptomatic women). DATA SOURCES: We conducted a literature search using the MEDLINE database from 1991 to 1997, and the key words "vaginal ultrasonography" and "endometrial thickness measurement." The review was limited to original research reports written in English, concerning symptomatic women having vaginal ultrasonography before a diagnostic test and not receiving tamoxifen. STUDY SELECTION: A total of 48 studies were identified. A questionnaire was sent to the corresponding author of each paper requesting supplementary information. Data were included in our analysis if the corresponding author was able to supply information on the median endometrial thickness in unaffected symptomatic women and the endometrial thickness values in affected women. Nine studies were thus included in our meta-analysis, representing 3483 women without endometrial cancer and 330 women with endometrial cancer. TABULATION, INTEGRATION, AND RESULTS: The median endometrial thickness in women with endometrial cancer was 3.7 times that in unaffected women at the same center, and with the same menopausal status and same hormone replacement therapy use category. The detection rate was 63% (95% confidence interval 58, 69) for a 10% false-positive rate, or 96% (95% confidence interval 94, 98) for a 50% false-positive rate. CONCLUSION: Endometrial thickness measurement in symptomatic women does not reduce the need for invasive diagnostic testing because 4% of the endometrial cancers would still be missed with a false-positive rate as high as 50%.