This study analyzed the proximate compositions, total amino acids, and fatty acid compositions in muscle and viscera of 51-month-old triploid and diploid Pacific abalone, Haliotis discus hannai. Proximate composition analysis showed that the muscle of diploid abalones had a higher protein and ash ratio than that of triploid abalones, while there was no significant difference in the ratios of moisture and fat (P>0.05). The triploid abalones had a significantly higher ratio of carbohydrate in muscle than the diploid abalones (P<0.05), which suggests that the transference of carbohydrates from muscle to gonad is decreased in sterile triploid organisms. Amino-acid analysis indicated that the total content was 133.42 mg/g in diploid muscle and 151.46 mg/g in triploid muscle. Taurine, arginine, glutamine, glycine, glutamic acid, alanine, and leucine, which are the major amino acids in abalone, were measured as 84.64 mg/g in triploid muscle and as 73.92 mg/g in diploid muscle. The essential amino acid content of triploid muscle (38.83 mg/g) was significantly higher than that of diploid muscle (31.94 mg/g) (P<0.05). Saturated fatty acids and monoene fatty acids were abundant in triploid muscle and polyene fatty acids were abundant in diploid muscle. Therefore, triploid Pacific abalone appears to be a good nutritional food source.