Male very-low-birthweight (VLBW) infants are more prone than females to health and developmental problems and less positive mother-infant interactions. Because gender differences in brain development and social relationships suggest hormonal influences on quality of mother-infant interaction, the authors explored the associations of maternal and infant salivary testosterone and cortisol levels with mother-infant interactions in the sample as a whole and by gender, after controlling for covariates. Data were collected prospectively from 62 mothers and their VLBW infants through infant record review, maternal interview, biochemical measurement of both mothers and infants, and observation of mother-infant interactions at 40 weeks postmenstrual age and at three and six months corrected age. Infants' positive interactions increased and mothers' decreased from three to six months. In generalized estimating equation (GEE) analyses, after controlling for covariates, higher maternal testosterone and infant cortisol were associated with more positive and more frequent maternal interactive behaviors. In GEE analyses by infant gender, after controlling for covariates, effects of maternal and infant hormone levels became more significant, especially on infants' interactive behaviors. Based on these preliminary findings, among VLBW infants, males with high testosterone are expected to have less positive mother-infant interactions than males with low testosterone or female infants. (C) 2015 Wiley Periodicals, Inc.