Background: Increase in skin colonization of Staphylococcus aureus (S. aureus) in atopic dermatitis patients (AD) resulted from the reduction of cathelicidin production in these patients plays the important role in pathogenesis of this disease. Recently in vivo study has showed that vitamin D can stimulate cathelicidin production. Oral supplement of vitamin D might be beneficial in atopic dermatitis. Objective: To determine the effect of oral vitamin D supplement on clinical impact including skin colonization of S. aureus in atopic dermatitis patients.