Many people have opinions on abortion, but relatively few contribute a substantial amount of time and effort to actively support their causes. This study investigated factors associated with level of activism in the abortion movement. The issue was addressed from a cost-benefit framework based on theory and research from other social movements. In a sample drawn from pro-life and pro-choice organizations, activism was related to attitude salience, attitude polarization, social ties to abortion activists, and agentic self-esteem. Potential constraint variables (e.g., employment) and social approval from important others showed little relation to activism. Factors affecting activism were similar for pro-choice and pro-life activists. Findings were generally consistent with studies of political activism for other social causes.