Although it has been established that the offspring of alcoholics are themselves at increased risk for alcoholism, there is a lack of accepted markers of that risk. The proposed research will investigate the hypothesis that measures of postural steadiness provide a marker, and in addition will investigate the specific effects of acute and chronic alcohol consumption on balance mechanisms. Postural control will be studied using a dynamic posturography instrument (EquiTest, Neurocom Int.) which provides for systematic challenges to balance. This instrument will offer significant advantages over the methods that have been used in prior studies, which have consisted of measures of static ataxia rather than dynamic balance control mechanisms. The instrument measures the contributions of the visual, proprioceptive and vestibular systems to balance, and also measures motor righting responses elicited by perturbations of the platform surface. Convergent information regarding vestibular function will be obtained from a comprehensive battery of measures of oculomotor function, including positional and gaze nystagmus, optokinetic response, and pursuit and saccadic movements. Measures of postural control and eye movements will be studied in four experiments involving different groups of subjects. Subjects will be drawn from an on- going study of the genetics of alcoholism (Collaborative Study on the Genetics of Alcoholism), which provides for systematic ascertainment and assessment procedures. Experiment 1 will study preadolescent children of both sexes, with subject groups stratified according to familial density of alcoholism (and presumed accompanying risk). It is hypothesized that the children of alcoholics will show balance impairments, due in part to an over-reliance on visual sensations, and that these impairments will be in proportion to the familial density of alcoholism. Experiment 2 will investigate the dose-related effects of acute alcohol on posturographic and ocular motility measures, in young adult social drinkers. Experiment 3 will investigate the effects of alcohol challenge doses in groups of nonalcoholic male and female subjects formed on the basis of familial density of alcoholism and current levels of consumption. It is hypothesized that alcohol will exacerbate existing balance deficits in the offspring of alcoholics. Experiment 4 will study abstinent male and female chronic alcoholics, as a function of familial history, and age-matched control subjects. It is hypothesized that the postural control abilities of alcoholics will reflect the combined effects of familial and consumption histories. In all experiments the measures will yield evidence regarding the specific mechanisms involved in control of balance and the effects associated with alcohol.