AbstractAdrenocortical function and social behaviors were measured in 48 laboratory‐born juvenile monkeys in stable (original) groupings at rest, in the same groupings in competition for drinking water, in newly formed groupings each composed of animals from the same original dominance position, and upon return to the original groupings, always in groups of four. In newly formed groupings, plasma cortisol measured higher with each step down in the new dominance hierarchy, the effect attenuating by day 8. Although the partial correlation between frequencies of hostility behavior and plasma cortisol level was low (r = 0.05) when holding fear constant, the partial correlation between cortisol and fear behaviors, holding hostility behavior constant, was 0.86. The data provide evidence that corticosteroid elevations during social stress are related to behavior suggestive of fear and not aggression and are dependent upon dominance rank, the level of dominance competition, and previous dominance histor