Background and Aim: Atopic dermatitis is a chronic inflammatory skin disease whose prevalence has increased in the last few decades. It is a multifactorial disease and, in addition to genetic factors, various environmental factors are important in the picture the present study was designed to investigate prevalence of atopic dermatitis and its risk factors in 2-5 year old children at the kindergartens of Birjand city. Materials and Methods: In this case–control study, all 2-5 year olds (810 cases) at the kindergartens of Birjand city were assessed using Hanifin & Rajka criteria. After diagnosing afflicted children, in order to identify risk factors of the disease, 100 of them from the same kindergarten-without atopic dermatitis-were randomly selected as the control group. Both groups were matched with respect to age and sex. A self- designed questionnaire, consisting of 25 questions about risk factors of the disease, was used to collect information. The obtained data was analyzed by SPSS software (V 15) using T-test, Chi- square and logistic regression. Results: Prevalence of atopic dermatitis in children was 14.3%.of which 15.8% were females and 15.6% were over 4 years old. Mean age of feeding on cow milk and eggs was lower in the case group. (P=0.04, P=0.03, respectively).There was a significant association between keeping domestic animals and cigarette smoking in the habitation and atopic dermatitis (OR=3.35, CI=1.17– 9.62, 0.95 OR=3.58 CI=1.13– 11.41, 0.95 respectively). Conclusion: In prevalence of atopic dermatitis, the role of some risk factors including early supplemental nutrition, particularly feeding on cow milk and eggs, cigarette smoking and keeping domestic animals in the habitation are determinative.