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The reproductive success of an individual plant is in part a function of its capacity to assimilate resources, and this in turn is partially a result of plant morphology. Simmondsia chinensis, jojoba, a dioecious desert shrub, is dimorphic in secondary sexual characters in some desert populations, where females on average have larger leaves and more open canopies than males. The function of this sexual dimorphism was examined by investigating the importance of shoot morphology to reproductive components of plant fitness. The reproductive behavior of individuals tended to be associated with different morphological attributes for both males and females. Males with more ’’male-type’’ morphology tended to have more inflorescences and a greater likelihood of flowering than did males structured more like females, though they also had smaller inflorescences. Females with more ’’female-type’’ construction produced more flower buds in one of the study years and also produced heavier seeds than females with more male-like structure. Females from four different morphological classes allocated 1.5-4.5 times as much to reproduction as did males, but showed wide variability in whether or not they set fruit. Therefore females either had a much higher or a much smaller reproductive allocation than most males. Fruit set in the population studied is not limited by pollen availability, but is presumably constrained by abiotic resource availability. The asymmetry between sexes in the morphology of reproductively more successful individuals points to a potential for a resource-based evolutionary origin of sexual dimorphism in jojoba, arising from different morphological optima for each sex.