ABSTRACT: Possible roles of pheromones in inducing spawning of 2 brittle stars, Ophiocoma dentata and Ophiocoma scolopendrina, were tested with gonad homogenates. In both species, the ovary homogenate induced conspecific, competent males tospawn. The potential pheromone was species- specific and had no effect on conspecific females. The testis homogenate did not have any effect. Of the males 50% could be induced at an estimated concentration of 7.8 × 10^–7 gml^–1 (wet ovary weight/seawater) with a threshold concentration at 10^–8 g ml^–1. Some males could be induced to spawn at least 3 consecutive times at 1 d intervals. The unidirectional induction, i.e. malesinduced by female releasate, suggests high selective pressure of sperm limitation in these 2 species.