Two studies were conducted to determine the relationship between variability in acoustic features of the infant cry and medical risk factors. In study 1, 3 groups of preterm infants (healthy, sick and CNS pathology) were compared with term infants at 40 weeks gestational age. The cry was analyzed by computer. The coefficient of variability of cry amplitude and the formant features of the cry differed among the groups of preterm infants. In study 2, 3 groups of term infants at low, moderate and high levels of hyperbilirubinemia were compared on the cry measures. More variability in the formant features of the cry was found in infants with higher levels of bilirubin. The correlation between the coefficient of variation in the cry formants and level of bilirubin was statistically significant. These two studies suggest that variability in the acoustic features of the cry relate to the medical status of the infant and may provide a measure of neurophysiological integrity.