The nucleotide sequences of the cloned human salivary and pancreatic alpha-amylase cDNAs correspond to the continuous mRNA sequences of 1768 and 1566 nucleotides, respectively. These include all of the amino acid coding regions. Salivary cDNA contains 200 bp in the 5'-noncoding region and 32 in the 3'-noncoding region. Pancreatic cDNA contains 3 and 27 bp of 5'- and 3'-noncoding regions, respectively. The nucleotide sequence homology of the two cDNAs is 96% in the coding region, and the predicted amino acid sequences are 94% homologous. Comparison of the sequences of human alpha-amylase cDNAs with those previously obtained for mouse alpha-amylase genes (Hagenbuchle et al., 1980; Schibler et al., 1982) showed the possibility of gene conversion between the two genes of human alpha-amylase.