{Gynodioecy, the occurrence of hermaphroditic and female plants within the same population, has been hypothesized to promote outcrossing. This presumably confers an advantage on the offspring through the benefits of heterosis, the avoidance of inbreeding depression, or both. I tested this hypothesis by comparing offspring of gynodioecious Silene vulgaris. Seeds of self-fertilized hermaphrodites, cross-fertilized hermaphrodites, and cross-fertilized females were obtained by artificial pollinations of field plants. Four hundred randomly selected seed were weighed, sown without bias in a mist bed of a constant temperature greenhouse. For six weeks, I recorded germination daily, height weekly, and determined leaf number, area and biomass at the end of the experiment. Seeds of outcrossed females were significantly heavier than those of the selfed or outcrossed hermaphrodites (.9226 vs. .8414 vs. .8115 mg, respectively