Serum amyloid A1 (SAA1), the predominant isotype of acute phase SAA in plasma and the predominant precursor of fibrillar deposits in reactive amyloidosis, is encoded by a gene, for which six allelic variants have been described. Recent studies proposed that the allele SAA1.3 was positively correlated with the development of reactive amyloidosis in Japanese. This study examined whether the plasma concentration of total SAA is influenced by specific SAA1 alleles. Two hundred and eighty healthy Japanese subjects were examined to determine the allelic distribution of SAA1 and SAA2 genes by the PCR-RFLP method, and to measure the total plasma SAA concentrations. SAA concentrations were significantly higher (p < 0.001) in subjects with the allele SAA1.5 than those without it, suggesting that SAA1.5 may have a distinctive feature in the process of synthesis or catabolism. Subjects with the allele SAA1.3 had lower SAA concentrations, though not statistically significant, than those with SAA1.1. There was not significant correlation of SAA2 alleles with SAA concentrations. These results are discussed in terms of amyloidogenicity.