The heart rates of rats aged 4, 7, and 12 days were recorded for control (CG), undernourished (UG), control-handled (CHG), and undernourished-handled (UHG) groups after exposure to amyl acetate and menthol. Pregnant dams were undernourished and received 50% of a balanced diet from gestational day (G) 6 to G12, 60% from G13-G18, and 100% from G19-G21. On postpartum days 0-12, pups remained for 12 h with a normal and 12 h with a nipple-ligated dam. The pups were handled 5 min daily on days 1-12 of age to ameliorate the stress from undernourishment. Basal heart rate, heart rate habituation, and the discrimination to a second odor were evaluated. Body weight of UG and UHG rats was significantly reduced. Basal heart rate gradually increased with age, especially in the CHG, without changes in the UHG; habituation was present and odor discrimination was modified by the diet and handling. These data indicate that olfactory discrimination is present at birth, and undernourishment does not impair but handling modifies its functionality.