ABSTRACT: Linkage of measures of the adequacy, content, and quality of prenatal care with pregnancy outcome is a long-standing research challenge. We attempted to improve on prior studies by developing a measure of prenatal care that encompasses the specific items thought to mediate its relationship with birthweight and by then examining the association of this measure with birthweight. An eight-item index of prenatal care was used to abstract information from the medical records of 63 white and 56 black women who gave birth to low-birthweight (<2500 g) infants and 61 white and 101 black women who gave birth to normal-weight (3000 + g) infants in 1987 at two Kaiser Permanente facilities. In univariate analyses the mean values for the index were higher in controls than in cases for both black and white women, but the difference was statistically significant only for blacks. In multivariate analysis the index was not significantly associated with the risk of low birthweight for whites or blacks. Prenatal care was extremely homogeneous in this population, which compromised the evaluation of the index as a correlate of low birthweight. We believe that this is a promising method for assessing the content of prenatal care and studying the association between content and outcome of care.