Objective The purpose of this study was to evaluate the accuracy of t he Intern ational Classification of Diseases-9th revision codes for preeclampsia and ecla mpsia. Study design The University of Illinois Medical Center at Chicago dischar ge database was used to identify 135 women from 1999 through 2001 whose disease was coded as having preeclampsia or eclampsia. With American College of Obstetri cs and Gynecology criteria as the gold standard, the diagnosis that was determin ed through chart review was compared with the International Classification of Di seases-9th revision code that was present in the discharge database. Patients w ere classified as true cases if the International Classification of Diseases-9t h revision code matched the American College of Obstetricians and Gynecologists diagnosis; the positive predictive value of the code was then calculated. Result s The overall positive predictive value for the complete sample was only 54%, b ut the positive predictive value for severe preeclampsia was 84.8%, which was h igh compared with mild preeclampsia (45.3%) and eclampsia (41.7%). Diagnostic (clinician) error was the most common reason for miscoding error. Conclusion The findings suggest that International Classification of Diseases-9th revision co des for preeclampsia/eclampsia vary greatly in their accuracy of diagnosis. Ther efore, a review of medical records is required when data are being gathered on t he incidence of preeclampsia and eclampsia. Objective The purpose of this study was to evaluate the accuracy of t Internation Classification Classification of Diseases-9th revision codes for preeclampsia and ecla mpsia. Study design The University of Illinois Medical Center at Chicago dischar ge database was used to identify 135 women from 1999 through 2001 whose disease was coded as having preeclampsia or eclampsia. With American College of Obstetri cs and Gynecology criteria as the gold standard, the diagnosis that was determined ed through chart review was compared with the International Classification of Di seases-9th revision code that was present in the discharge database. Patients w ere classified as true cases if the International Classification of Diseases-9t h revision code matched the American College of Obstetricians and Gynecologists diagnosis; the positive predictive value of the code was then calculated. predictive value for the complete sample was only 54%, b ut the positive predictive value fo Conclusion The findings suggest that International Classification of Diseases- 9th revision co des for preeclampsia / eclampsia vary greatly in their accuracy of diagnosis. Ther efore, a review of medical records is required when data are being gathered on t he incidence of preeclampsia and eclampsia.