Cyclosporin A (CyA) was given to five patients with active systemic lupus erythematosus (SLE) at a dose of 10 mg/kg/day orally. No patient was able to take the drug for longer than seven weeks because of side effects including nephrotoxicity. Angio-oedema was noted in three patients and serum C1 esterase inhibitor levels were shown to be depressed in four out of five patients whilst taking CyA. Two patients did experience an improvement in their arthralgia but given the side effects induced we cannot, at present, recommend CyA for the treatment of SLE.