Growth and home-orienting behavior were studied during the 1st 12 days of life in 3 groups of rat pups: (1) those with intergenerational malnutrition; (2) those with postnatal malnutrition produced by cross-fostering pups born of well-nourished mothers to lactating females maintained on a low-protein diet; and (3) well-nourished control pups. Growth of pups was impaired in both malnourished groups, and eye-opening was similarly delayed. On tests of homing behavior, both malnourished groups were impaired to a similar extent and were less likely to find their way to the nest than were control pups. However, survival rates were significantly lower (50%) in the postnatally malnourished group but not in the intergenerationally malnourished group (73%), as compared with controls (100%). These findings suggest that adaptation occurs in long-term malnutrition with increased survival. However, physical characteristics and homing behavior in early life are not distinguishable in those surviving short- or long-term malnutrition. This is in contrast to the finding of more severe behavioral deficits in later life among rats subjected to many generations of malnutrition than among those malnourished for only 1 generation.