The floral biology, nectar production behavior, floral visitors, and reproductive systems of Jatropha ribifolia (Pohl) Baill. (Euphorbiaceae) is presented and compared of those of J. mollissima (Pohl) Baill. and J. mutabilis (Pohl) Baill. The study was undertaken in an area of hyperxerophilous caatinga at the Estação Biológica de Canudos, Bahia State, Brazil, from May 2005 to June 2007. The flowers of the three species are disposed in a protogynic dichasium. In J. ribifolia both staminate and pistilate flowers last for about 48 hours and flower opening is diurnal, while in J. mollissima and J. mutabilis the staminate flowers last from 12 to 15 hours and the pistilate flowers from 36 to 48 hours, with flower opening occurring at sunset. Nectar production, pollen viability, and stigma receptivity initiate soon after full opening of both floral types, and sexual activity overlaps until senescence. Nectar production varied throughout the day, with higher production by the pistilate flowers; pollen viability and stigma receptivity during the lifetime of the flower occurred in all three species. Significant differences occurred between the reproductive system treatments of J. mollissima (KW = 59.796), J. mutabilis (KW = 59.058), or J. ribifolia (KW = 63.660). The three species produced fruits by experimental geitonogamy as well as experimental xenogamy, while only J. ribifolia produced fruits by spontaneous geitonogamy. The bees Apis mellifera, Xylocopa frontalis and X. grisescens and the hummingbirds Chlorostilbon lucidus and Anopetia gounellei are potential pollinators for J. mollissima and J. mutabilis and A. mellifera and X. grisescens are potential pollinators for J. ribifolia. The diversity of anthophiles on flowers of the three species allows pollen flow and fruit set. On the other hand asynchronous flowering and differences of flower morphology and anthesis help maintain the reproductive isolation and prevent the loss of interspecific pollen due to sharing of pollinators.