The reproductive development of Asterias amurensis was investigated from December 2001 to October 2002 by gonadal histology and gonad index (GI) in Tongyeoung, southern part of Korea. In the ovary, growing oocytes were lined along germinal layer at various stages of development and oocytes accumulated rapidly yolk materials in January. The partially spawned and spent ovaries were observed in February and the actual spawning activity took place during the period form March to May with a maximum percentage (76%) in April. In 2001, peak female GI was recorded in April. Although this percentage was somewhat higher (70%) in May, spent stage reached to 40% comparing to 6% in April. The males exhibited a gametogenic pattern similar to that of the females, with partially spawned and spent testis prevalent in April and May with a high percentage (60% in both month). The GI and histological examination revealed that major spawning activity occurred in Tongyeong population from May.