OBJECTIVE: The purpose of this study was to examine associations of weight gain from prepregnancy to glycemic screening with glucose tolerance status. STUDY DESIGN: Main outcomes were failed glycemic screening (1-hour glucose result >or= 140 mg/dL) with either 1 high value on 3-hour oral glucose tolerance testing (impaired glucose tolerance in pregnancy) or >or= 2 high values on 3-hour oral glucose tolerance testing (gestational diabetes mellitus). We performed multinomial logistic regression to determine the odds of these glucose intolerance outcomes by quartile of gestational weight gain among 1960 women in Project Viva. RESULTS: Mean gestational weight gain was 10.2 +/- 4.3 (SD) kg. Compared with the lowest quartile of weight gain, participants in the highest quartile had an increased odds of impaired glucose tolerance in pregnancy (adjusted odds ratio, 2.54; 95% confidence interval, 1.25-5.15), but not gestational diabetes mellitus (odds ratio, 0.93; 95% confidence interval, 0.50-1.70). CONCLUSION: Higher weight gain predicted impaired glucose tolerance in pregnancy, but not gestational diabetes mellitus.