Abstract: The tip region of asparagus (Asparagus officinalis L.) spear, comprising immature, rapidly developing tissues, is particularly susceptible to harvest stress and is usually the first part of the spear to show several detrimental changes during storage. In order to define the factors contributing to postharvest deterioration, a 1-aminocyclopropane-1-carboxylate oxidase (ACC oxidase, pAS-ACO) cDNA clone was isolated from a cDNA library prepared from the tip section (apex to 33 mm) of the spears using reverse transcriptase-polymerase chain reaction. The partial cDNA clone encodes an mRNA of 832 bp and the derived amino acid sequence is highly homologous to ACC oxidase from rice, pea and cucumber. Northern blot analysis showed increase level of pAS-ACO mRNA until 3 d at 20oC, which coincided with ethylene production and the ACC oxidase activity, suggesting that the increase might be a response to the wounding associated with harvest.