This paper presents a model of how the supply of applicants for public employment programs may be determined, with the information necessary to incorporate the model factors into simulation of such programs. The methodology used to estimate the size and composition of the supply population for public employment programs--how many persons would have preferred public employment had that option been available to them--is outlined. The availability of jobs in a given public employment program, as well as the potential labor supply, is considered. The supply of applicants is positively related to wage differences but negatively related to differences in hours. Changes in public policy both in and out of the manpower area may also influence the supply of applicants. The methodology employed in this research is sufficiently flexible for adoption to various program characteristics. (MF)