Coordination of infants' suck-swallow-breathing patterns is integral to safe and efficient feeding. However, assessment of these patterns is difficult and often invasive, particularly in breast-fed infants less than 4 months of age. The aims of this study were to develop an ultrasound approach to visualize swallowing in term breast-feeding infants and to determine the accuracy of ultrasound imaging of swallowing compared to respiratory inductive plethysmography (RIP). On ultrasound, the breast milk bolus was observed as a predominantly echogenic area moving inferiorly. Of the 388 swallows detected with ultrasound, 379 correlated with the swallow apneas detected by RIP (R(2) = 0.98). The mean duration of the swallow was 0.63 +/- 0.06 s. Ultrasound imaging is a noninvasive accurate method for detection of swallowing by visualization of movement of the milk bolus through the pharyngeal area of a breast-feeding infant. These techniques may potentially provide useful information for infants experiencing breast-feeding difficulties.