Oxygen consumption at intermittent mandatory ventilation (IMV) rates of 10 and 20 breaths per minute was evaluated to determine whether a higher IMV rate in mechanically ventilated premature infants with apnea and respiratory insufficiency would reduce metabolic expenditure. Ten studies were performed in seven infants, with three infants studied twice after a trial of failed elective extubation. The mean birth weight was 952 +/- 183 kg (SD), and the mean postnatal age was 12 +/- 8 days (SD). Mean oxygen consumption per kilogram of body weight was not significantly related to pulmonary resistance, dynamic lung compliance, or resistive work of breathing. Mean oxygen consumption was not altered at the different IMV rates. The oxygen consumption difference at the two IMV rates was not significantly related to dynamic lung compliance, resistance, or work of breathing. These results demonstrate that mechanically dependent premature infants without bronchopulmonary dysplasia do not have significant alteration in oxygen consumption with changes in IMV. This finding suggests that there is no potential metabolic energy balance benefit in use of moderately higher IMV rates to achieve improved growth rates in this population of infants.