The technique of differential display was used to isolate ethylene-responsive cDNAs from the apices of cucumber plants. Differences in RNA populations from apices treated with or without ethephon (an ethylene - releasing compound) were examined using 80 primer combinations. Northern blot analysis confirmed that 20 cDNAs represented mRNAs that were differentially expressed upon ethephon treatment (promoted, 17; suppressed, 3). Sequence analysis of these cDNAs revealed that two clones were identical to the 3′-terminal regions of the CR20 and CUS3 genes of cucumber. Five clones showed significant similarity to the C-terminal regions of short-chain alcohol dehydrogenases, β-1,3-glucanases, S-adenosyl-L-methionine:salicylic acid carboxyl methyltransferase, products of the Aux/IAA gene family, and lipoxygenases. The other 13 clones were found to have no significant homology in the databases. Because ethylene promotes female flower formation in cucumber plants, some of 20 cDNAs might be involved in processes of sex regulation.