The risk of predation and cost or benefit of a mating attempt are rarely the same for both sexes. An excellent example is provided by the guppy, Poecilia reticulata, a species that has a promiscuous mating system in which female choice plays an important role. Males engage almost continuously in courtship behaviour but, as females are sexually receptive for short periods only, most male displays are ignored and sneaky mating attempts avoided. Experiments on guppies from wild Trinidad populations reveal that females appear to perceive themselves to be at a greater risk of predation and devote more time to anti-predator behaviour, for example, schooling when threatened. Inspections of the predator are also mainly initiated and led by female guppies. Males exploit this behavioural switch by increasing their sneaky mating attempts. A game theoretical analysis is used to explore the sexual asymmetry in mating cost and predation risk. Together these approaches show that there is no intersexual cooperation during predator inspection behaviour in this species, and may explain the paradoxical increase in mating activity by male guppies under threat.