During the past year, our research included studies of: (1) neurobiology and behaviors that are correlated with Type II- like excessive alcohol consumption, including aggression, impulsivity, sleep and activity deficits, and reduced affiliative social behavior. These studies show that males with low CSF 5- HIAA concentrations continue to die at higher rates than subjects with high CSF 5-HIAA concentrations. They are also not sought as sexual partners by females, and inseminate females at a lower rate than males with high CSF 5-HIAAA concentrations. Of particular interest is a finding that males with low CSF 5-HIAA concentrations exhibit high rates of physical aggression, and ultimately become high in social dominance ranking. This later finding suggests that reduced serotonin turnover, as measured by low CSF 5-HIAA concentrations, and physical aggression may be adaptive under certain conditions in some environments. (2) genetic influences on low CSF 5-HIAA concentrations. DNA were obtained from 150 males to assess the rate that males with low and high CSF 5-HIAA concentrations produce offspring. (3) long- term continuity of interindividual differences in CSF 5-HIAA concentrations. These studies show that like personality and temperament individual differences in CSF 5-HIAA concentrations are stable across time, and across a number of different environmental situations. Subjects with low CSF 5-HIAA concentrations continued to show low CSF 5-HIAA across repeated samplings from 18 months of age through their sixth year of life. Studies of females macaques first sampled in the naturalistic island environment showed that individual differences in CSF 5- HIAA concentrations were positively correlated between the island conditions, a single-cage, and a new social group environment two years later. This finding suggests that individual differences in CNS serotonin functioning is trait-like, showing interindividual stability across time and setting. (4) acquisition of social dominance in females removed from the naturalistic environment. Unlike the males studied above, in the absence of their family members, our studies showed that females with high CSF 5-HIAA concentrations were more likely to build friendships and coalitions which eventually led to high social dominance. Aggression was not correlated with social dominance. High rates of wounding were negatively correlated with CSF 5-HIAA concentrations.