We have examined the effects of exposure to chronic maternal anemia, throughout the final one-third of gestation, on postnatal ventilatory and arousal responses to hypoxia, hypercapnia, and combined hypoxia-hypercapnia in sleeping lambs. While resting quietly awake, lambs from anemic ewes had higher arterial PCO₂ levels than control animals during the first 2-3 postnatal wk, but pH, arterial PO₂, and arterial O₂ saturation were not different. During active and quiet sleep lambs from anemic ewes had higher end-tidal CO₂ levels than control animals when breathing room air and at the time of spontaneous arousal or when aroused by progressive hypercapnia or by combined hypoxia-hypercapnia. Ventilation and arterial O₂ saturation during uninterrupted sleep and ventilatory responsiveness to hypoxia (inspiratory O₂ fraction, 10%), progressive hypercapnia, and combined hypoxia/hypercapnia were not significantly affected by exposure to maternal anemia. Our findings show that maternal anemia results in elevated PCO₂ levels in the offspring. This effect may be due, at least in part, to altered pulmonary function.