Tacrolimus and cyclosporin A are potent immunosuppressants that are used systemically to treat several inflammatory skin conditions successfully. They differ in their structure and tacrolimus is 10-100 times more potent than cyclosporin A. They have similar side-effects. They have been used topically in various clinical studies. Topical cyclosporin A is largely ineffective whereas topical tacrolimus is effective in treating atopic dermatitis. Topical tacrolimus has not been studied sufficiently in treating psoriasis although it has been used successfully in allergic contact dermatitis, erosive mucosal lichen planus and pyoderma gangrenosum.