Experiments were carried out to determine if prior exposure to hypoxic-induced apnea impairs protective responses of newborn rats. Ninety-five, 5 to 6 day-old rat pups were instrumented for respiratory measurements and placed prone in a metabolic chamber regulated to 37.0°C. The time to first and last gasp as well as the number of gasps were determined upon exposure to unrelenting hypoxia after each pup had experienced 0, 1, 2, 3, 4, 9 or 14 hypoxic-induced apnea / autoresuscitation cycles (HIA/AR) at 5-minute intervals. Prior exposure to HIA/AR did not significantly alter the time to first gasp but it decreased the time to last gasp after two HIA/AR and the number of gasps after three HIA/AR upon exposure to unrelenting hypoxia. When the normoxic recovery time following 9 HIA/AR was varied from 5 to 120 minutes, the time to last gasp as well as the total number of gasps increased upon exposure to unrelenting hypoxia but only at 120 minutes (i.e., the number of gasps was similar but the time to last gasp was still decreased compared to that observed in naive animals exposed to unrelenting hypoxia). Thus, prior exposure to hypoxic-induced apnea as may occur during obstructive sleep apnea or positional asphyxia decreases the number and duration of potential autoresuscitation producing gasps upon exposure to unrelenting hypoxia for a period of up to and exceeding 120 minutes, respectively. The mechanism by which prior exposure to hypoxic-induced apnea influences the duration and number of hypoxic-induced gasps is unknown.