1,25-Dihydroxyvitamin D(3), the active form of vitamin D, is a major regulator of the expression of the cationic antimicrobial peptide cathelicidin, not only in monocytes but also in epidermal keratinocytes. The involvement of cathelicidin in wound healing and skin diseases as diverse as psoriasis, rosacea, and atopic dermatitis may create new opportunities for the use of vitamin D in dermatology.