ABSTRACT In this study we tested relations among personality characteristics, social network properties, and perceived social support both concurrently and prospectively. A sample of 294 men in treatment at a Department of Veterans Affairs Alcohol Treatment Unit was assessed during treatment and 3 months after discharge. Results of the cross-sectional structural equation analyses indicated that the personality characteristics of extraversion and neu-roticism were related to both social network properties and perceived social support. Characteristics of the alcoholic's social network were also related to perceived availability of support. Longitudinal analyses of perceived social support after treatment indicated that two social network properties (size of the network and the proportion of confidants) were predictive net of initial levels of social support. Extraversion and neuroticism were found to be indi-rectly related to perceived social support at Time 2 through their effects on social network properties and perceived social support during treatment. Implications of these findings for models of the nature and determinants of perceived social support are discussed.