We report the insecticidal efficacy of Jatropha curcas seed oil against two bruchid beetle species, Callosobruchus maculatus Fab and Bruchidius atrolineatus Pic, devastating stored cowpea seeds (Vigna unguiculata). J. curcas oil concentrations ranging from 0.0, 0.25, 0.5, 1.5, 2.5, 5.0 and 7.5 ml were mixed with 200 g of cowpea seeds before introduction of 10 pairs (5 males and 5 females) of C. maculatus or B. atrolineatus as the case may be. Mortality, fecundity and rate of emergence were observed and compared with untreated control and a standard (Deltamethrin). J. curcas oil reduced adult survival in both species, B. atrolineatus being more sensitive than C. maculatus. Oviposition was also reduced by 85 to 90% in the females of both species after exposure to 2.5 ml of J. curcas oil solution. Only 9% of C. maculatus nymphs emerged as adults in seeds treated with 2.5 ml of oil. In B. atrolineatus, emergence was reduced to 12% in seeds treated with 1.5 ml of oil.