Healthy amphioxi with 4cm average body length were selected, divided into three groups: female group, male group, and female plus male group (female: male=1:1), and cultured from 8 July 1996 to 11 August 1997. It was found that (1) Majority of the animals in all the three groups formed fully- developed gonads; (2) Amphioxi in both female and male groups failed to spawn during the breeding season, but those in the female plus male group spawned as their field counterparts; (3) Fertilized eggs from the female plus male group developed normally. Apparently, complete separation of the female from the male did not influence the gonadal development but influenced the spawning. Possibly, spawning in the amphioxi might involve sex pheromonal control.