Dietary modification to achieve weight loss during the postpartum period may be critical for prevention of obesity, particularly in low-income, minority women. The aim of this cross-sectional study was to develop and validate a measure to examine motivations to eat in low-income, minority women during early postpartum. A convenience sample of 179 triethnic women was recruited from the Special Supplemental Program for Women, Infants, and Children clinics from June 2004 to April 2007. Subjects made one visit to a study center where they completed the Eating Stimulus Index and questions regarding individual demographic characteristics including ethnicity, age, income, education, marital status, breastfeeding, and employment status. Weight and height were also measured during this visit and used to calculate body mass index (BMI; calculated as kg/m(2)). An additional sample of 31 women completed the Eating Stimulus Index on two occasions with 2 weeks between to establish test-retest reliability. The factor structure of the scale was examined with principal components analysis. Total scale scores and subscale scores were calculated and Pearson's correlation and multiple regression analysis examined relationships to BMI. Principal component analysis produced an eight-factor structure with loadings >0.40. Cronbach's alpha coefficients for each subscale ranged from .54 to .89. Subscales of Convenience Eating, Emotional Eating, and Dietary Restraint were related to BMI in mothers. African-American, exclusively formula-feeding, and older women were most vulnerable to convenience eating. White women and those with the highest level of education were most vulnerable to emotional eating. The Eating Stimulus Index is a valid and reliable instrument with the ability to discriminate by weight. It can be used to assess motivations to eat in order to facilitate development of tailored weight-loss messages during early postpartum.