This study explored the role of three theoretically important interpersonal variables in attempted suicide and unintentional overdose using a diverse sample of one hundred thirty-one (69 women) methadone patients at an urban university hospital. Subjects completed a standardized interview including self-report measures of perceived 1) belonging 2) burdensomeness, and 3) loneliness. In separate multivariate logistic regression analyses, individuals with a history of attempted suicide were compared to non-attempters, and individuals with a history of unintentional overdose were compared to individuals without such a history. As hypothesized, low belonging distinguished suicide attempters but not individuals with a history of unintentional overdose, after accounting for covariates. Results concerning burdensomeness and suicide attempt were also suggestive. Findings underscore the relevance of a sense of belonging to vulnerability to suicidal behavior, and lend further support to the notion that suicide attempts and unintentional overdose have dissimilar correlates.