To investigate molecular changes during the ripening of oriental melon (Cucumis melo var. kuwata) and to isolate a fruit-specific, ripening up-regulated gene, differential screening was done. 8 cDNAs corresponding to mRNAs whose abundance were increased during ripening were isolated, among them were 1-Aminocyclopropane-1-carboxylate oxidase (ACC OXIDASE), Abscisic acid, stress, ripening regulated gene homologue (ASR gene), and polyubiquitin. The other cDNAs showed no significant homology with known protein sequence. The expression pattern and genomic structure of a cDNA clone which showed homology with ASR gene was characterized. Expression of isolated ASR homologue was fruit specific, and could be detectable during Immature Green stage, increased till Ripe stage, and slightly decreased during Over Ripe stage. Southern blot analysis revealed there are low copies of ASR gene homologue in oriental melon genome. Full cDNA sequence of ASR gene homologue was obtained by Rapid Amplification of cDNA End.