Diploid (2n) and cold-shocked triploid (3n) Asian catfish Clarias macrocephalus at eight months of age were comparatively studied by initially examining the cytological appearances of erythrocytes under a light microscope, an Epifluorescence microscope, and a scanning electron microscope (SEM). It was found that while the size of erythrocytes from triploids including their nuclei were larger than the diploids, cell density in the triploids was lower than cell density in diploids having the values of 1.57 ± 0.05 x 107 cells/ml blood and 1.03 ± 0.04 x 107 cells/ml blood, respectively. When lipid contents were assessed it was found that flesh of triploids contained 6.26 ± 0.52 g lipid/100g tissue which was significantly higher than the value of 5.37 ± 0.47 g lipid/100g tissue in diploids (p<0.01). Analysis of protein content showed that triploid catfish contained 18.93 ± 0.88 g protein/100g tissue which was about the same level as the value of 18.58 ± 0.31 g protein/100g tissue in diploid catfish (p>0.05). When the average amount of lipid and protein were considered per individual fish it was evident that triploids had significantly more lipid, as well as more protein than diploids. This was in agreement with the fact that the triploid fish were significantly bigger than the diploid fish. Analysis of proteins by SDS-PAGE revealed that triploids and diploids contained the same pattern of proteins, having molecular weights ranging from 18.6 – 120.2 kD. Also, both triploid and diploid Asian catfish did not exhibit the 12.5 kD protein band, the well-known Gad cI allergen protein of codfish. This finding would assure consumer confidence in taking Asian catfish as part of the protein source. Detailed investigation of fatty acid composition showed that both diploids and triploids contained substantial amount of the two important omega-3 fatty acids, the eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The values for EPA and DHA were 14.5 ± 4.5 and 130.5 ± 48.2 mg/100g tissue in diploids, and 38.5 ± 12.4 and 134.8 ± 50.1 mg/100g tissue in triploids, respectively. These finding implicates the Asian catfish as an important and economical source for omega-3 fatty acids. When lactate dehydrogenase (LDH) activities in fillet, kynurenine (a tryptophan metabolite) in plasma, and variable number tandem repeat (VNTR) specific for apolipoprotein B in DNA isolated from nuclei of blood cells were analyzed, it was found that there were no differences in those parameters between diploid and triploid Asian catfish.