Infantile hypertrophic pyloric stenosis (IHPS) is a condition affecting infants in the first few months of life. The condition is manifested by persistent vomiting and is caused by a hypertrophied muscle obstructing the gastric outlet. The condition is treated by pyloromyotomy. The incidence is 1-8/1000 births and varies among different populations. The etiology of IHPS is unknown, but both genetic and environmental factors are thought to contribute to the disease. Genetic linkage analysis has so far localized five loci that could harbor genes contributing to IHPS. The only gene implicated in IHPS is the nitric oxide synthase gene (NOS1), in which a single nucleotide polymorphism (rs41279104) in the promoter region has been associated with the disease in 16 patients. In this study, we examined an association of this SNP in 54 familial and 28 sporadic cases with IHPS, and compared the results with normal controls using univariate and multiple logistic regression analysis. We could not confirm any association between the analyzed SNP and infantile hypertrophic pyloric stenosis.