alpha-Farnesene is a volatile sesquiterpene in the natural coating of apple fruit. Oxidation products of this sesquiterpene are thought to induce superficial scald in apple. A cDNA encoding a-farnesene synthase converting farnesyl diphosphate to a-farnesene was obtained by using RT-PCR from peel of apple fruit (Accession No. AY563622). Comparison of the sequence of the cDNA with AFS-1 gene registered in the GenBank (AY182241) showed that these sequences shared high similarity in nucleotide sequence and homology in deduced amino acid sequence. Southern blotting suggested that there was only one copy in the genome of apple. Northern blotting showed that the AFS gene played a key role in a-farnesene synthesis during the 10 days after apples were removed from cold storage and warmed to room temperature. Expression of the AFS gene was influenced by treatment with DPA and 1-MCP.