Himes, S. L. (Department of Biology, Western Carolina University, Cullowhee, NC 28723) and R. Wyatt (Highlands Biological Station, 265 Sixth Street, P.O. Box 580, Highlands, NC 28741). Costs and benefits of self-fertility in Asclepias exaltata (Apocynaceae). J. Torrey Bot. Soc. 132: 24–32. 2005.–Variation in levels of self-fertility exists among populations of Asclepias exaltata, despite traditional characterization of this species as self-sterile. The costs and benefits associated with self-fertility were investigated by comparing fruit-set, seed number, and progeny fitness from self-pollinations, single-donor cross-pollinations, and multiple-donor cross-pollinations. Single-donor cross-pollinations were expected to produce fewer fruits than multiple-donor cross-pollinations as a result of mate selection by maternal plants, but this was not the case. Outcrossed fruits from self-fertile plants contained significantly fewer seeds than did outcrossed fruits from self-sterile plants, but overall fitnesses of self-fertile and self-sterile plants were essentially equal. There was variability among self-fertile plants in their propensity to mature selfed fruits, but, on the whole, selfed fruit-set was very low compared to outcrossed fruit-set. Furthermore, seed number, percent seed germination, and plant survival were significantly lower for selfed versus outcrossed progeny on self-fertile plants, suggesting strongly that selfed progeny suffer greatly from inbreeding depression. Because selfing is rare and the overall fitnesses of self-fertile and self-sterile plants are essentially equal, frequencies of self-fertile individuals in these populations may differ simply due to random processes.