OBJECTIVE: To determine the population-based incidence of hypertensive diseases in pregnancy in Western New York. METHODS: A database of 77,358 women with singleton pregnancies was analyzed using birth certificate data. The incidence of pregnancies complicated by gestational hypertension, preeclampsia, and eclampsia was determined. RESULTS: The overall incidence of pregnancy-associated hypertensive disease varied slightly from 1999 to 2003. The incidence of preeclampsia decreased from 1.8% to 1.1% (p < 0.01). This decrease persisted over time, despite controlling for known risk factors, such as body mass index, age, ethnicity, parity, smoking, diabetes, and chronic hypertension. CONCLUSION: The incidence of pregnancy-related hypertensive disorders slightly decreased in our population in the last 5 years, with a decline in the rate of preeclampsia accounting for this change. Further analysis may provide additional insights into the population-based incidence of preeclampsia.