Recurrent hyperemesis gravidarum is a frustrating and poorly studied complication of early pregnancy. Between 1979 and 1987, 140 women with emesis severe enough to require parenteral fluid and electrolyte replacement were admitted to the Medical University of South Carolina Hospital, Charleston, on 220 occasions. Thirty-nine of the 140 women were admitted on multiple occasions. A comparison of clinical characteristics of women with single and multiple admissions revealed no significant differences except that women admitted repeatedly for hyperemesis gravidarum were more likely to be nulliparous (P less than .05). Ptyalism (59% vs. 9%) and persistent vomiting for greater than 24 hours after admission (69% vs. 23%) were significantly more common among women who were admitted repeatedly (P less than .05). Despite published reports that hyperemesis gravidarum has no impact on ultimate perinatal outcome, this study indicated that women admitted repeatedly have a more severe nutritional disturbance, associated with significantly reduced maternal weight gain and neonatal birth weight. These risks argue for more aggressive antenatal treatment and increased fetal surveillance in pregnancies complicated by recurrent hyperemesis gravidarum.