The estimates of genetic diversity based on 7 polymorphic loci coding for 6 isozymes were compared between the tolerant and the sensitive trees in an air polluted Prunus sargentii stand located on Ulsan industrial area. Although we could not observe statistically significant differences in allele and genotype frequencies between the two groups except the gene locus Got-2, the unique alleles and genotypes were observed in the tolerant group. All the genetic parameters such as genetic multiplicity, genetic diversity, and heterozygosity revealed that a greater amount of genetic variations existed in the tolerant group.