Immunodiagnostic potential fractions in fluke antigens and excretory/secretory (E/S) antigen of F. gigantica have been identified using double immunodiffusion (DID), immunoelectrophoresis (IEP) and sodium dodecyl sulphate (SDS) PAGE electrophoresis. Hyperimmunised rabbits elicited considerable level of antibody response with few precipitin lines showing reaction of identity in DID suggesting presence of some common fractions in all antigens. Mature fluke somatic (MFSAg) and immature fluke somatic (IMFSAg) antigens showed exactly similar pattern of precipitin lines in both DID and IEP. Antibodies to experimentally infected rabbits with F. gigantica were also detected by DID using MFSAg and E/S antigens at 4 weeks post infection. However, out of 6-7 fractions obtained from Sephadex G-200 column chromatography in MFSAg and IMFSAg antigens only F3, F4 and F5 along with E/S antigen were able to detect antibodies by DID. Mature fluke and E/S antigen separated out in 9 bands in the range of 12 to 95 kDa and 5 bands in the range of 12 to 29 kDa respectively of which proteins of molecular weight 12, 15, 18, 28 and 29 kDa were common in both antigens. Therefore, it appears that immunodiagnostic fractions of antigens may be present in between 12 and 29 kDa.