Rat pups (Rattus Norvegicus) were exposed to saccharin through suckling dams whose drinking water had been adulterated during lactation. Behavioral evidence is reported that the saccharin penetrated the milk and was detectable by the pups. Preexposure to saccharin did not influence the effects of taste aversion training conducted with a saccharin CS when the pups were 18 days old. Taste aversion learning was weaker in the pups than in adults run in the same study. No effect was found for CS concentration on taste aversion learning for the pups or the adults. / M. S.