I examined the number of lifetime mating opportunities and mating behaviour of males in two sexually cannibalistic species, the Mediterranean, Iris oratoria, and bordered, Stagmomantis limbata, praying mantids (Mantodea: Mantidae). Two approaches estimated the number of lifetime mating opportunities: direct observations of intersexual encounters in the field, and an encounter model. I collected behavioural observations, together with ecological data for use in the model, over three field seasons. The ecological data included an assessment of the feeding condition of S. limbata females in nature; the females fed at a level comparable to females maintained on an abundant diet in the laboratory. As for the number of mating opportunities, individual males of both species encountered two or more females, as predicted by the model. I observed no male, however, in more than one copulation. This result could reflect individual variation in the times and places of sexual activity or an actual low number of mating opportunities in the field. Furthermore, a higher percentage of I. oratoria males encountered two or more females than S. limbata males, as the model indicates. Fewer mating opportunities could lead to greater selection upon S. limbata males to ensure paternity at each mating, which can explain the longer copulation times observed for S. limbata males. I considered two hypotheses about male behaviour in light of the number of lifetime encounters with females: male suicide and male reduction of the risk of cannibalism. Behavioural observations do not strongly support male suicide in either species. Certain male behaviours, such as the nature of copulatory position and, in captivity, mounting females from the rear, are consistent with the idea that males behave so as to reduce the probability that they are cannibalized during intersexual encounters. Moreover, male I. oratoria preferentially mount well-fed, fecund females in captivity. Taken together, these results suggest that the prospect of multiple mating opportunities has influenced male mating behaviour over evolutionary time. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.