Although allergic asthma and allergic rhinitis have recently been considered to be a single disease, many questions remain unanswered. Why do some atopic patients develop asthma symptoms and others develop allergic rhinitis symptoms? Which factors play a role in the development of different allergic phenotypes? We hypothesized that angiotensin-converting enzyme (ACE) gene polymorphism might play a role in the development of asthma phenotypes in children with allergic rhinitis. The study sample included 106 children with allergic rhinitis, but no asthma, and 105 age- and gender-matched children with allergic rhinitis and asthma. Subjects of both groups exhibited the same systemic immunologic changes and allergen sensitivities. Controls consisted of 102 healthy children. The ACE genotype was determined by polymerase chain reaction. The serum total immunoglobulin E (IgE) level, allergen-specific IgE sensitivity, and eosinophil count were also measured. The frequencies of the DD genotype were significantly higher in the children with both allergic rhinitis and asthma than in the children with allergic rhinitis but no asthma [p = 0.018; odds ratio (OR) = 3.257; (1.222-8.680)]. Results of this study suggest that ACE gene polymorphism DD genotype might play a role in the development of the asthma phenotype in children with allergic rhinitis.