This study tests the proposition that selective behaviors of both mother and infant during feeding are predictors of weight gain during the first month of life. Forty normal mother-neonate pairs were studied, and the target behaviors were examined using an adaptation of the techniques developed by Brown and Bakeman (in which approximately 60 different mother behaviors and 40 different infant behaviors are coded). Two observers simultaneously coded the behaviors shown on videotapes of the mother-infant feedings. Aggregate scores of four specific maternal and infant behaviors accounted for more than 32% of the variance in total weight gain. These findings indicate that the availability of nutrients is not in itself a sufficient condition to meet the infant's nutritional needs. Implicit in these findings are the possibilities that infants at risk of failure-to-thrive can be identified, and measures to prevent this syndrome can be introduced. (Author/SB)