Part time work can facilitate participation in the labor market and smooth the transition to retirement. Part-time employment, however, represents for the most part an involuntary choice. The aim of this paper is to conduct an empirical investigation of the determinants of part-time work. Using Spanish labor market data, we find that parttime work becomes a more desired employment alternative as people age, and that education and children’s age have opposite effects on women and men’s probabilities of voluntary part-time employment. Interestingly, most part-time work among women occurs in low-skill occupations, whereas part-time work among men are mainly concentrated in high-skill jobs