BACKGROUND: It is suggested that the increasing prevlence of atopic disease may be derived from the changes of environmental factors. We evaluated the recent changes of atopic prevalence and the major cusative allergens. METHOD: 422 Seoul National University medical students were enrolled in this study from 1990 to 1994. Skin prick tests with ten common inhalant allergens were carried out and atopy was defined if the wheal size of one or more causative allergens were greater than that of control (wheal size of histamine minus saline) RESULTS: 1) The mean prevalence of atopy from 1990 to 1994 was 32.7% for recent five years. 2) The prevalences of atopy were 31% in 1990, 25% in 1991, 33% in 1993 and 40.8% in 1994. Especially, the prevalence of atopy has been increased significantly from 1991 to 1994(p<0.05). 3) D. farinae was the most prevalent allergen and D. pteronyssinus, cat fur, mugwort pollen, cockroach, rgweed pollen, tree pollen, grass pollen, Alternaria tenuis and, Asp. fumigatus were in order. 4) The sensitization rates of D. farinae were 17.2% in 1990, 20% in 1991, 24.6% in 1993 and 30.9% in 1994. CONCLUSION: The prevalence of atopy has been increased recently and D. farinae is the major contributable factor for this phenomenon.