BACKGROUND: Routine procedures are a large component of the caretaking day for preterm infants. Such procedures can have profound adverse effects on an infant's condition, to the point of disrupting normal growth and development. Despite this evidence, routine procedures are perpetuated in the neonatal ICU. OBJECTIVE: To determine the physiological and behavioral effects of a supposedly beneficial procedure, a sponge bath, on premature infants. METHODS: The study sample consisted of 14 preterm neonates with no neurological abnormalities at two tertiary neonatal ICUs. The ages of the subjects were 28.1 to 31.8 weeks postconception and 4 to 25 days after birth. The study was a prospective, quasi-experimental, repeated-measures design in which each infant acted as his or her own control. Oxygen delivery, heart rate, oxygen saturation, and behavioral responses were continuously recorded by computer or real-time videotape. Physiological and behavioral parameters were compared across three phases: 10 minutes before a bath (baseline), during a standardized bath, and 10 minutes after the bath. RESULTS: Physiological and behavioral disruptions occurred throughout the bath phase and in many cases beyond that phase. These disruptions included significant increases in heart rate, cardiac oxygen demand, and frequency of behavioral motoric cues. Significant decreases in oxygen saturation also accompanied the bath. Nine infants required increased concentrations of ambient oxygen. A significant association was found between physiological components and the frequency and timing of behavioral motoric cues. CONCLUSIONS: The results provide further evidence that routine care is not innocuous to neonates. Routine sponge bathing is not recommended for care of ill premature infants.