OBJECTIVES: The aim of this study was to compare the risk factors in women who delivered an infant of low birth weight (LBW, <2,500 g) versus women who delivered an infant weighing >2,500 g in a large metropolitan county (Bexar) in South Texas. DESIGN: An exploratory case comparison design was used to identify factors related to LBW outcomes in women receiving prenatal care. SAMPLE: The cases were obtained from community hospitals. A stratified random sample was selected from a population of 38,064 infant births, of which 2,910 were identified as LBW. The final sample size was N=321 (<2,500 g, n=151; >or=2,500 g, n=170). MEASUREMENTS: Dependent variable of infant birth weight; independent variables of maternal age, maternal race/ethnicity, education, smoking, prior pregnancy history, timing of and number of prenatal visits, prepregnancy body mass index and weight gain during pregnancy, and past medical history and medical problems during pregnancy. RESULTS: Independent variables found to be predictive of LBW in this study included maternal race/ethnicity, timing of first prenatal visit, number of prenatal visits, prior pregnancy history, and maternal weight gain. CONCLUSIONS: This study confirmed previous findings that African American women are at a higher risk for LBW deliveries and demonstrated that Anglo and Hispanic women have similar rates of LBW deliveries.