Cathepsin C is a member of the papain superfamily of lysosmal cysteine protease. Our previous studies showed that the expression of cathepsin C was involved in the final stages of oocyte maturation of the kuruma prawn (Marsupenaeuzs japonicus). In this study, the developmental process of the prawn oocytes was examined with light microscope and the cathepsin C activity was measured during oogenesis and final oocyte maturation. The prawn oocyte development was classified into 9 phases, which include (1) oogonium phase, (2) plasmosome phase, (3) peripheral nucleolus phase, (4) primary vitellogenesis phase, (5) secondary vitellogenesis phase, (6) early cortical rod phase, (7) middle cortical rod phase, (8) late cortical rod phase, and 9) ovulation phase. The germinal vesicle breakdown occurred before ovulation. Immunolgical blot analysis showed that cathepsin C protein was expressed exclusively at the cortical rod stages in final oocyte maturation. However, the cathepsin C activity was low and there was no significant difference at cortical rod stages as compared with noncortical rod stages, suggesting that cathepsin C might have a crucial role in regulating CR release and/or formation of a jelly layer during fertilization.