Seven-day-old rat pups were olfactory bulbectomized, cortical lesioned, or sham lesioned, tested for nipple attachment 24 hr after surgery, then housed with their dam and weighed daily for the next 7 days. On the basis of histological findings the bulbectomized animals were divided into two subgroups: Those with removal of all olfactory bulb tissue (n = 9) and those in which some cellular elements remained in the lesioned area (n = 7). There were no differences between sham and cortical lesioned groups for nipple attachment behavior or weight gain. The completely bulbectomized pups did not show nipple attachment, lost weight each day, became moribund and had to be sacrificed by the fifth postoperative day. Deficits in incompletely bulbectomized pups were somewhat less severe and each of these survived and maintained or gained weight in the latter part of the test period. These results suggest that suckling may be critically dependent upon olfaction in 8 day or older pups and that significant savings in this behavior may be mediated by small remnants of olfactory bulb tissue.