Abstract.1This study investigates sperm competition inCullosobruchus maculatus(F.) (Coleoptera: Bruchidae), and is the first study to make a direct, controlled comparison of the sterile male and genetic marker techniques to estimate sperm precedence.2P2values (the proportion of offspring fathered by the second male) obtained from the two methods were similar: P2(sterile male) = 0.82, P2(genetic marker) = 0.85. Both methods are therefore suitable for studying sperm precedence if the appropriate correction factors are applied.3The importance of general fertilization ability, differential fertilizing capacity and differential zygote mortality are examined and discussed.