Recently, we have reported that ovulated female masu salmon excrete L-kynurenine (Kyn) as a releaser pheromone for conspecific spermiating males. In this study, we tested a primer effect of ovulated female urine and Kyn to males. Blood sample and the expressible milt were collected before exposure and 3 hours after exposure. All test groups showed no significant effect on volumes of expressible milt. However, exposures to ovulated female urine (OFU) and Kyn induced significant elevations in plasma 17,20b-dihydroxy-4-pregnene-3-one (17,20b-P) concentrations 3 hours after introducing odours. We suggest that the urine of ovulated female masu salmon and Kyn had a primer effect.