The lack of agreement on specific tasks used by social workers who serve chronically and severely mentally ill clients precludes generalizations about the results of outcome and other studies. This study sought to determine if a common set of task dimensions could be identified that were used in serving this population in community mental health settings. Using 861 questionnaires from workers in mental health facilities in 11 southeastern states, task statement responses were factor analyzed. Cronbach's alpha was applied to determine reliability. Three factors, or "taxa," were identified: primary personal services (assessment, planning, treatment, and monitoring tasks), interface services (client identification and outreach, administration, public relations, and education and training tasks), and environmental (or secondary) personal services (advocacy and linkage tasks). This taxonomy provides a basis on which systematic empirical research can be conducted.