Our objective was to determine the effect of 1 year low-dose cyclosporine A (CSA) treatment on disease activity and renal involvement in systemic lupus erythematosus (SLE). Patients included in the pilot study had an active form of the disease as defined by the SLE Disease Activity Index (SLEDAI). Main organ involvement was represented by lupus nephritis classified in repeated renal biopsies. Eleven patients with SLE were enrolled in the study. In eight of them, previous therapy with cyclophosphamide or azathioprine had to be interrupted due to serious adverse reaction or low efficacy. Nine patients experienced clinical nephrotic syndrome, and two the nephritic syndrome. After 12 months of CSA treatment, the mean SLEDAI score had decreased significantly from 26.18 to 4.00 (P < 0.01). Similarly, the titre of antinuclear and anti-dsDNA antibodies had dropped significantly (P < 0.01). Proteinuria decreased rapidly from 9.10 to 1.70 g/24 h (P < 0.001). According to the WHO classification of renal biopsies, three patients had their class altered from IV to III in response to CSA treatment and five patients had changed the status from the high severity grade to the mild. The adverse reactions included hypertension (45%), gingival hyperplasia (18%) and hirsutism (9%). No significant increase in serum creatinine or any CSA related toxic changes were found in renal biopsies. The favourable response observed in patients with active SLE and with major renal involvement strongly suggests that low-dose CSA is a potent drug as much for the reduction of the disease activity as for lupus nephropathy treatment.