An analysis of the literature on renal toxicity of long-term cyclosporin A (CsA) in auto-immune diseases reveals that besides functional renal toxicity also de novo morphological kidney damage can be induced already after 12 months with low dose (< or = 5 mg CsA/kg/day). In the early stage the findings are light changes. However, after two years treatment they are light to moderate. In a blinded study on 30 patients with psoriasis, including 18 with psoriatic arthritis, the severity of findings increased with length of therapy, and after four years all but one had arteriolar hyalinosis, with interstitial fibrosis pronounced in five and moderate in six of eleven patients, and at the same time glomerular sclerosis had become significant. The data presented indicate the necessity of an evaluation of the risk-benefit ratio for each patient. Accepted guide-lines should be strictly followed, and after two years treatment a rotation to other therapies, or a careful following by glomerular filtration rate (GFR) together with sequential renal biopsies should be considered.