Reproductive behavior of the sandperch Parapercis snyderi was studied in the coastal waters of Shikoku Island, Japan. This fish is a monandric and protogynous hermaphrodite. Males maintained home ranges of ca. 10 m(2) that slightly overlapped with each other. Harems included on average 2.45 females that were spaced out from each other. Males mated successively in pairs with the harem members within two hours before sunset. To release gametes, the pair rushed upward 10-200 cm. The pair spawning was sometimes parasitized by sneaking of an adjacent harem master, which had usually finished mating with his own mates. More than 80% of the sneaking rushes reached the apex of the pair rise, suggesting a high success rate of sneaking. Such sneaking by harem masters has not been reported in the genus Parapercis. The comparative reproductive ecology of this genus suggested that sneaking in P. snyderi is due to the close proximity of adjacent harems.