The methodologic study addressed the validity of subjective, physiologic, behavioral, and maternal indicators of pain intensity among 149 preschoolers who received immunizations at four clinics in the Southwest. Instruments used to measure children's responses included the Global Mood Scale (GMS) to measure anxiety, apical heart rate to measure physiologic response, the Wong and Baker Faces Scale to measure psychologic response, and the Children's Hospital of Eastern Ontario Pain Scale (CHEOPS) to measure behavioral response. The visual analogue scale (VAS) was used to measure mothers' perceptions of their children's pain. Results demonstrated correlations ranging between r = .27 to r = .44, p < .01 among the child's physiologic response to pain, the child's behavioral activity, and the mother's perception of pain. Correlations ranged from r = .26 to r = .30, p < .01, n = 144 among the child's verbal report of pain as measured by the Faces Scale, the mother's perception of pain, and the child's behavioral activity. The child's behavioral activity, mother's perception, and change in heart rate correlated positively with the child's anxiety. Children discriminated between anxiety and pain using the Faces Scale. More than one method may be required to fully assess the pain intensity experience by young children.