A recent study has demonstrated the possible involvement of a leukotriene C4 synthase (LTC4S) gene polymorphism in ASA-intolerant asthma (AIA) in a Polish population, whereas no significant association was noted in other populations. To investigate the role of genetic polymorphism in AIA development, we screened single nucleotide polymorphisms (SNPs) of the key enzymes involved in arachidonate metabolism, and the cysteinyl leukotriene receptor 1 (CYSLTR1) in a large Korean population with AIA: 93 AIA and 181 ASA-tolerant asthma (ATA) patients, and 123 normal controls. The single-base extension method was used to genotype SNPs in 5-lipoxygenase (ALOX5, -1708G-->A, 21C-->T, 270G-->A, 1728G-->A), ALOX5-activating protein (ALOX5AP, 218A-->G), prostaglandin-endoperoxide synthase 2 (PTGS2, COX2, -162C-->G, 10T-->G, R228H, V511A), LTC4S (-444A-->C), and CYSLTR1 (927T-->C). Haplotype analyses were undertaken for the SNPs in ALOX5. No significant differences in allele and genotype frequencies of single SNPs were observed between the patient groups ( P>0.05). However, the frequency of the ALOX5-ht1[G-C-G-A] haplotype in the AIA group was significantly higher than its frequency in the ATA group with a probability ( P) of 0.01, odds ratio (OR) of 5.0, and 95% confidence interval (95%CI) of 1.54-17.9, and in the normal controls ( P=0.03, OR=4.5, 95%CI=1.1-18.4), by using a dominant model. These results suggest a lack of association between the ALOX5AP, PTGS2, LTC4S, and CYSLTR1 gene polymorphisms and the AIA phenotype in the Korean population. However, the possible involvement of ALOX5-ht1[G-C-G-A] in AIA development is suggested.