Apple is a typical climacteric fruit, whose loss of firmness during storage is associated with internal levels of ethylene. MdACS1 (1-aminocyclopropane-1-carboxylate synthase) and MdACO1 (1-aminocyclopropane-1-carboxylate oxidase) genes are characterized well as functional markers for the ethylene production of ripening apple fruit. Presence of two alleles for each gene are commonly reported in cultivated apples. MdACS1-1/1, 1-1/2 and 1-2/2 generally induce high, medium, and low ethylene production, respectively. Homozygosity of MdACO1-1 resulted in low levels of ethylene production than MdACO1-1/2 and 1-2/2. It was reported that cultivars homozygous for MdACS1-2 and MdACO1-1 had superior shelf-life with lowest ethylene production. In this study, genotypes of 42 apple cultivars including Korean-developed ones at MdACS1 and MdACO1 loci were determined. Polymorphisms were detected by PCR and were separated by electrophoresis in a 2.0% agarose gel. Of PCR products of MdACS1, the fragrament of 490 bp was corresponded to the MdACS1-1 allele and 640 bp corresponded to the MdACS1-2 allele. ACO1-1 and ACO1-2 alleles had the fragment size of 525 and 587 bp, respectively. The 42 cultivars could be grouped into three classes to each gene, MdACS1-1/1, MdACS1-1/2 and MdACS1-2/2; MdACO1-1/1, MdACO1-1/2 and MdACO1-2/2.