The detection and avoidance of parasitized males has been proposed to be a component of female mate choice. We investigated whether or not female laboratory mice, Mus musculus domesticus, could discriminate between parasitized and non-parasitized males on the basis of odour. Female mice were given a choice between the urine and other odorous secretions of either a male mouse sub-clinically infected for five days with the naturally occurring, enteric, single host, protozoan parasite, Eimeria vermiformis, or an uninfected male. Females showed a marked preference for the odours of non-parasitized male mice over those of the parasitized males; as measured by number of investigations, time spent per investigation, and total investigation time of the odours in a choice situation. Female mice also displayed an overwhelming initial, or first choice, preference for the odours of the non-parasitized male mice over those of the parasitized males. These observations show that female mice can distinguish between the odours of parasitized and non-parasitized males, and discriminate against parasitized males on the basis of odour. We suggest that the detection and avoidance of infected males by female mice through odour cues may function to reduce parasite transmission and potentially serve as a component of female mate selection or choice.