Sexual dimorphism in the dioecious plant Asparagus officinalis L. was examined by two-dimensional (2-D) electrophoresis of both total proteins and newly synthesized proteins from cladophylls (leaves), whole mature flowers and homologous sex organs (i.e. true female ovaries and small sterile ovaries from male flowers). Polypeptides isolated from cladophylls of male and female plants were practically indistinguishable; the flowers, however, showed a distinct set of specific proteins, some of which differed between the two sexes. While the total protein profiles of isolated ovaries from male and female plants were very similar, the patterns were strikingly different after the tissues were pulsed with 35S-methionine: mature male ovaries showed a number of newly synthesized proteins, while in female ovaries only a few molecular species were actively synthesized.