This exploratory-descriptive study examines the association between social functioning and subclassifications of manic-depressive illness in family constellations with presumed genetic vulnerability for affective illness. The research question is: Are there differences in the social functioning of family members with bipolar I disorder, bipolar II disorder, and their biological relatives who are not affectively ill? A study sample of convenience was drawn from the Genetic Linkage Study of Affective illness conducted at the Johns Hopkins University School of Medicine. Twenty-one bipolar I's, 22 bipolar II's, and 20 unaffected participants were included. Instruments included interviewer administered scales (Hamilton Depression Rating Scale, Young Mania Rating Scale, and Health and Daily Living Assessment) and self administered scales (Social Adjustment Scale SR and Eysenck Personality Questionnaire). As hypothesized, findings reveal a statistically significant relationship between the diagnosis of bipolar illness and inadequate social functioning in the areas of close social relationships and overall social role adjustment. Both the bipolar I's and the bipolar II's had significantly fewer close relationships than their biological unaffected relatives. The two bipolar groups did not differ significantly from each other. When analyzed by Multiple Regression, personality as measured by the Eysenck Neuroticism Scale was found to be more highly predictive of overall social role adjustment than was the diagnosis of bipolar illness. Implications for social work and related practice in mental health settings and further research were drawn. Conceptual refinement of the global concepts social functioning within the interpersonal field and normality is greatly needed. Knowledge is lacking in the areas of nosology and the psychological and social environments which characterize individuals with subclassifications of bipolar illness. The impact of both ill and well intervals upon the family system needs to be explored.