Preterm infants' physiological indicators, such as heart rate, respiratory rate, and oxygen saturation levels, are routinely monitored by devices that can alert nurses to threatening changes in condition. Most Neonatal Intensive Care Units use standard criteria as alerting algorithms to determine when an alert should be issued, and these standard criteria have been adopted uncritically in studies of preterm infants. This article presents results from a study examining preterm infants' physiological responses to a gentle human touch (GHT) intervention in which we compared the use of standard and individualized criteria to define the percentages of abnormally low and high heart rates (HRs) and abnormally low oxygen saturation (O 2 sat) levels before, during, and after periods of GHT. Results indicated that there were no differences in the percentages of abnormal HRs or O 2 sat values between periods using standard criteria. However, using individualized criteria, there were significantly greater percentages of abnormally low heart rates and O 2 sat levels during and after GHT periods as compared to baseline periods. The findings suggest that standard criteria may not be sensitive enough to detect subtle physiological responses to environmental stimuli such as touch. Moreover, consistent with the recognition of the value of individualized developmental care, these results suggest that the clinical effectiveness of individualized criteria for setting monitor alert limits merits further investigation.