It has been suggested that different forms of organizational commitment have different outcomes as well as different antecedents. To test the hypothesis that instrumental attachment to an organization is associated with members' investments in the organization, and that affective attachment to an organization is influenced primarily by the way the organization treats its members (a process of reciprocation), professional and paraprofessional hospital employees (N=727), and bank clerical employees (N=154) were tested. Subjects completed Porter's Organizational Commitment Questionnaire; measures of instrumental attachment, job satisfaction, and personal attributes; and a measure of existence, relatedness, and growth needs. Multiple regression analyses and simple correlation were used to measure differential relationships between the two forms of attachments and two types of antecedents. Mixed support was found for the relationship between instrumental attachment and committing investment, and affective attachment and reciprocation with the organization. The development of measurement instruments specifically designed to sort out different forms of attachment may be required. (MCF)