Avoidance conditioning during pregnancy, changes in caretaker behavior during lactation, and changes in offspring catecholamine levels and behavior were investigated in C57BL/6J mice. Three equal groups of mice were employed. One group was avoidance conditioned prior to pregnancy and continued to avoid shock during pregnancy; a 2nd group was avoidance conditioned during pregnancy; and the 3rd group served as untreated controls. Offspring were crossfostered after birth. During lactation the proportion of time the caretaker spent on the nest was observed. At weaning pups were individually housed. Offspring dopamine concentrations were measured in the corpus striatum at birth and at days 22 and 42 of age. Their performance was evaluated in the open field at Day 42 of age. The results showed that mice receiving avoidance conditioning prior to parturition were more likely to cannibalize their offspring at parturition than were control animals. Furthermore, preparturiently avoidance conditioned mice spent less time on the nest if they reared offspring from biological mothers who had been avoidance conditioned when compared to similarly treated caretakers who reared offspring from untreated control biological mothers. Regardless of postnatal experiences, adult offspring from avoidance conditioned biological mothers had significantly reduced levels of dopamine in tissue from the corpus striatum and were significantly less active in the open field when compared with offspring from control biological mothers. Behavioral results support the findings of others that the prenatal environment plays an important role in shaping the later behavior of offspring. The decrease in dopamine levels suggests that avoidance training as one form of psychosocial stimulation during pregnancy can be disruptive to the development of the dopamine regulatory mechanisms.