INTRODUCTION: We compared the gestational weight gains of black and white women with the 2009 Institute of Medicine (IOM) recommendations to better understand the potential for successful implementation of these guidelines in clinical settings. METHODS: Prenatal and birth data for 2760 women aged 18 to 40 years with term singleton births from 2004 through 2007 were abstracted. We examined race differences in mean trimester weight gains with adjusted linear regression and compared race differences in the distribution of women who met the IOM recommendations with chi-square analyses. We stratified all analyses by prepregnancy body mass index. RESULTS: Among normal-weight and obese women, black women gained less weight than white women in the first and second trimesters. Overweight black women gained significantly less than white women in all trimesters. For both races in all body mass index categories, a minority of women (range 9.9%-32.4%) met the IOM recommended gains for the second and third trimesters. For normal-weight, overweight, and obese black and white women, 49% to 80% exceeded the recommended gains in the third trimester, with higher rates of excessive gain for white women. DISCUSSION: Less than half of the sample gained within the IOM recommended weight gain ranges in all body mass index groups and in all trimesters. The risk of excessive gain was higher for white women. For both races, excessive weight gain began by the second trimester, suggesting that counseling about the importance of weight gain during pregnancy should begin earlier, in the first trimester or prior to conception.