The effects of skin-to-skin contact on three indexes of energy expenditure: heart rate, activity level, and behavioral state, were examined in a pilot study. It was hypothesized that skin-to-skin contact, because of its soothing effects, would increase sleep, lower activity level, and reduce heart rate. Eight healthy preterm infants in a neonatal intensive care unit, who had reached 34 to 36 weeks gestation, experienced one session of skin-to-skin contact for an interfeeding interval. Observations were made once each minute using continuous videotape throughout three consecutive interfeeding intervals (before, during, and after skin-to-skin contact). Significant treatment effects were found by repeated-measures analysis of variance for behavioral state and activity level; pair-wise comparisons showed that quiet sleep frequency was significantly increased and activity level reduced during skin-to-skin contact. Infants had longer durations of quiet sleep during skin-to-skin contact. The Pearson product-moment correlation between heart rate and behavioral state was robust and generally linear, supporting use of heart rate as a measure of energy expenditure in these subjects. The findings suggest that skin-to-skin contact is a simple, cost-effective intervention that reduces activity and state-related energy expenditure.