The majority of research on organizational commitment has focused on commitment in traditional, ongoing and open-ended relationships. The commitment of employees in non-standard work arrangements such as temporary employment has been subject to much less theoretical and empirical investigation. In this study, we examine the affective and continuance commitment of temporary workers towards their agency and its determinants. We distinguish two groups of determinants: the process by which the temporary worker chose a particular agency and the support provided by the agency. The findings can be summarized as follows: (1) affective commitment among temps is generally higher than their continuance commitment; (2) having more alternative agencies to choose from (i.e., volition) does not enhance the commitment of temporary workers; (3) a public choice for a particular agency raises both types of commitment, whereas the perceived agency dependence created by the choice increases continuance, but not affective commitment; and (4) both types of commitment are positively influenced by agency supportiveness, reflected in the way the agency deals with problems, the career support it provides, and the way it keeps in close contact with its temporary workers. Finally, the results suggest that factors raising affective commitment may 'spill over' to increase continuance commitment.