The psychological model of organizational commitment (OC) has been extensively investigated in U.S. workers (Near, 1989), but less frequently applied in cross-personality studies. The investigation proposes a model of turnover intentions (TI) that uses locus of control (LOC) as a moderator. A causal model and a firm-specific sample were used to compare the different personality traits of LOC. Considered as a case study, this research surveyed a sample of professional and managerial personnel in a service-based commercial bank in Taiwan. The antecedent examined was perceived organizational support (POS); job satisfaction and OC were mediating constructs. Test results indicated a stronger influence of job satisfaction on TI and OC among those with an internal lOC than those with an external LOC. However, the influence of POS on job satisfaction and OC was stronger among externals than internals. Finally, the Influence of OC on TI was similar in both internals and externals. The implications of these findings are discussed.