The authors tested indicators of effective breastfeeding to identify those that provide reliable estimates of human milk intake. Human milk intake of 82 full-term infants was measured by test weights before and after feeding and compared with commonly used breastfeeding indicators: rooting, length of time before latch-on, latch-on, suckle, observable swallowing, and audible swallowing. Two models were tested: model 1, describing indicators at 96 hours postpartum, and model 2, describing indicators at >96 hours postpartum. Median (interquartile) milliliters of mother's milk consumed per feeding was 26 ml (range, 4-47) at 96 hours and 54 ml (range, 26-73) at >96 hours. Significant predictors of human milk intake in model 1 were rooting and observable swallowing (R2=26%, P<.01). In model 2, audible swallowing alone estimated human milk intake (R2=29%, P<.001). Observed swallowing and rooting during the first 4 days (96 hours) following birth and audible swallowing after that time should be included in the breastfeeding assessment of full-term infants.