For evolutionary reasons, pollen production is expected to be modified when changes occur in plant mating systems. In this study, outcrossing was enforced through male-sterility in usually autogamous populations of winter wheat. The correlated changes in pollen production were studied after a 6-year period of natural evolution. Both the disappearance of individuals with the lowest pollen production and the increase in the production of fertile pollen per spike were observed in male-fertile plants. The results are interpreted as a selection on male function. Some morphological differences also appeared in evolved populations between male-fertile and male-sterile plants. These differentiations are discussed in light of resource allocation theory.