The relationship between testosterone and alcohol's effects on social behavior within established groups of squirrel monkeys was studied. Consistent behavioral differences between dominant and subordinate monkeys were quantitatively measured using computer assisted, continuous measurement techniques. Blood samples collected during the mating season revealed plasma testosterone measures of 202.9 +/- 13.4 ng/ml in dominant monkeys and 28 +/- 6.2 ng/ml in subordinate monkeys. Alcohol (0.1-1.0 g/kg, PO) produced a dose-related decrease of testosterone levels in dominant monkeys. Concurrently, alcohol produced biphasic effects on the behavior of dominant but not subordinate monkeys; low doses (0.1, 0.3 g/kg) increased the frequency of threats, grasps, and displacements. Subordinate monkeys were not affected at any dose. During the non-mating season, plasma levels of testosterone fell to 55.2 +/- 23.7 ng/ml in dominant monkeys and 7.3 +/- 1.7 ng/ml in subordinate monkeys. Plasma testosterone and the social behavior of both dominant and subordinate monkeys were unaffected by alcohol. These findings provide further evidence of a specific association between alcohol, testosterone and aggression in the non-human primate. High levels of testosterone that are evident during the mating season of dominant, male squirrel monkeys may activate alcohol sensitive brain substrates of aggressive behavior.