This study investigated the relationship between work history and partnership formation for British men. Two questions were asked: (i) Do instabilities in young men's careers lead to a higher probability of entering into cohabitation and, in turn, to a postponement of first marriage? (ii) Are there cohort differences in the effects of men's careers on their partnership decisions? The analyses were based on data from two birth-cohort studies for men born in 1958 and 1970. The results suggest that highly unstable occupational careers make it very likely that young men's first partnership is a cohabitation rather than a marriage. Further, having an unstable occupational career early in working life is a strong impediment to transforming cohabitation into marriage. Finally, there is no evidence of a weakening between cohorts of the effects of men's work careers on their partnership decisions.