Background: 5-Lipooxygenase (ALOX5) and 5-lipoxygenase-activating protein (ALOX5AP) are known as key enzymes in cysteinyl-leukotriene (cys-LT) production, critical mediators in aspirin acetylsalicyclic acid (ASA)-intolerant asthma (AIA). To date, studies of the promoter region of ALOX5 gene has revealed the potential influence of a variable number of tandem repeats of a Sp1- and Egr1-binding motif, on the transcription rate. Methods: To understand the pathological process that arises from cys-LT overproduction in AIA, we genotyped ALOX5 Sp1 and ALOX5AP poly(A) repeat promoter polymorphism by fluorescent-based capillary electrophoresis in the Korean population. Results: No significant differences in allele and genotype frequencies of the ALOX5 and ALOX5AP promoter polymorphisms were observed between the three groups. However, there was a strong association of the ALOX5 Sp1 repeat polymorphism with airway hyperresponsiveness (AHR; PC₂₀ methacholine); AIA patients carrying a mutant allele (n > 5 or n