This research was conducted to identify the character of vtg and its differential expression in the hard-lipped barb (O. hasselti C.V.).  The vtg protein were isolated from sera of adult females, adult males and adult males injected with 17β estradiol.  The sera were subjected to SDS-PAGE with stacking gel of 5% and resolving gel 10%.  The specific band observed in adult females and adult males treated with 17β estradiol but absent in nomal adult males was considered as vtg candidates.  The band were exised from the gel and purified from the polyacrilamide gel using electroellution. The purified protein, the vtg were then used to immunised male mice to induce anti hard-lipped barb vtg antiserum. The specificity of antiserum was confirmed using dot blot and immunohistochemistry. The differential expression of vtg was performed using immunohistochemistry on the sections of juvenile ovaries, actively reproductive ovaries, normal and 17β estradiol treated testis and their respective livers. The samples were collected according to purposive sampling method. The results showed that there are two vtg protein in the hard-lipped bard, the molecule of 45kDa and 117kDa.  The 117kDa vtg consentration in the serum was 0,98 µg/µL in adult female, and 1,31 µg/µL in 17β estradiol-treated male.  The 45kDa vtg protein was undetected in the female but it was detedted in 17β estradiol-treated male as much as 0,83 µg/µL.  The dot blot confirmed that the protein was vtg.  Differential expression study showed that the antisera against 117kDa vtg as well as 45kDa vtg was detected in the vitellogenic oocytes with diameter >333µm and post vitellogenic oocytes but undetected in the previtellogenic oocytes nor testicular tissues.  At the extragonadal sites, the vtg was detected in the hepatocytes, sinusoid and the hepatic vein of adult female and 17β estradiol-treated males but undetected in juvenile females nor nomal adult males.