Summary Background Epidemiologic studies have suggested that helminth infections play a protective role against allergy; this inverse association, however, has not been consistent. Clonorchis sinensis, the liver fluke of human, is prevalent in the Far East. The association between C. sinensis infection and allergy has not yet been reported. Objective We evaluated the association between clonorchiasis and atopy or allergic diseases in adults in endemic areas of clonorchiasis. Methods A total of 1116 subjects (males 419, females 697; age range, 30–86; mean age=61 years) were recruited from two endemic areas of C. sinensis in Korea. Clonorchiasis was confirmed by stool examination. Allergic symptoms were evaluated with a modified ISAAC questionnaire, and atopy was defined by skin prick test for common inhalant allergens. Total serum IgE and C. sinensis‐specific IgE level was measured by ELISA and methacholine bronchial provocation test was performed to evaluate airway hyperresponsiveness (AHR). Results Clonorchiasis was positively associated with atopy odds ratio (OR), 1.856; 95% confidence interval (CI), 1.199–2.873 and high levels of total serum IgE (OR, 1.455; 95% CI, 1.050–2.016). Higher association with clonorchiasis was shown in subjects who showed both atopy and high total serum IgE levels (OR, 2.540; 95% CI, 1.448–4.455). Clonorchiasis had no association with wheezing, AHR, asthma or allergic rhinitis. Conclusion and Clinical Relevance Clonorchiasis was positively associated with atopy in adults in endemic area. Cite this as: M‐H Choi, Y‐S Chang, M. K. Lim, Y. M. Bae, S‐T Hong, J‐K Oh, E. H. Yun, M‐J Bae, H‐S Kwon, S‐M Lee, H‐W Park, K‐U Min, Y‐Y Kim and S‐H Cho, Clinical & Experimental Allergy, 2011 (41) 697–705.