Evidence bearing on the hypothesis that participation by the poor in social action organizations results in personal change is inconsistent and open to diverse interpretations. This paper first reviews that evidence and then takes the first step toward a substantive reconciliation of the apparently inconsistent evidence - the development of a typology of social action organization forms. The typology, which is derived from the literature on poverty and organizational analysis, incorporates the elements of (1) inclusion of the poor, (2) resource base of organizational sponsors, and (3) output goal orientation. The typology will be used in Part I I to order and interpret case study evidence of the participation hypothesis.