The etiology of postpartum eclampsia and hypertension remains controversial. Recent reports have suggested a possible idiosyncratic hypertensive reaction associated with the use of bromocriptine mesylate. The purpose of this study was to determine whether bromocriptine, used for lactation suppression, is a risk factor for postpartum hypertension. In 1813 consecutively delivered staff patients, blood pressures at three separate home visits were obtained between 3-21 days postpartum. Postpartum hypertension, defined for the purposes of this study as systolic pressure of 140 mmHg or greater and/or diastolic pressure of 90 mmHg or greater on any of the three home visits, was the dependent variable; bromocriptine exposure was the independent variable. Covariates included age, race, chronic hypertension, pregnancy-induced hypertension, and antihypertensive medication. Discriminant analysis, including the first-order interactions, revealed that race, history of chronic hypertension, pregnancy-induced hypertension, and antihypertensive medication contributed significantly to postpartum hypertension (F (7, 1803) = 107.9; P less than .001, explained variance 30%). Of all the interaction terms, only the bromocriptine by pregnancy-induced hypertension interaction was significant. These findings support the contention that patients with antepartum pregnancy-induced hypertension who receive bromocriptine for lactation suppression are at increased risk for postpartum hypertension. Avoiding the elective use of this drug in patients with pregnancy-induced hypertension might constitute a reasonable clinical response to these findings.