Cucurbita argyrosperma, formerly known as C. mixta, is a squash species native to Mexico and Central America. Cultivars of the species which have been grown in the United States include many of the cushaws and the `Silverseed Gourd. A recent biosystematic analysis-which included studies of experimental and natural hybridization, isozymatic and morphological variation, ethnobotany, and ecological and geographical distribution-has shown that the closest relative of C. argyrosperma is C. moschata. The data reveal intriguing implications for evolution of the genus as a whole, since the previous hypothesis that C. lundelliana is the progenitor of C. moschata is refuted. A wild ancestor, three cultivated varieties and a feral derivative are recognized within C. argyrosperma. Two of the three cultivated botanical varieties-vars. argyrosperma and stenosperma -have been selected in many regions almost exclusively for seed production. The relatively large seeds are marketed either with or without hulls. The other botanical variety, var. callicarpa, has been selected for both fruit and seed production. Northern cultivars of var. callicarpa arc notable for their adaptation to marginal environments, including hot climates and poor soil conditions.