Thirteen patients with chronic intraocular inflammation which had not been adequately controlled with oral prednisolone entered into an open study of low-dose Cyclosporin A (mean 4.1 mg/kg/day) combined when required with oral prednisolone (15 mg prednisolone per day or less). The mean duration of treatment was 26 months (range 8-44) over a mean follow-up period of 29 months (range 8-49). Visual acuity improved overall in ten patients, and remained stable in three. Six patients have completed a course of Cyclosporin A therapy, and four of these patients have retained their visual improvement. Two have returned to the pretreatment level of vision. Only one patient has required conversion to alternative immunosuppressive therapy. The mean serum creatinine concentration had increased significantly by 26% after six months (p less than 0.05) and 32% after one year (p less than 0.01) but remained stable during the subsequent 18 months. Four patients developed hypertension requiring hypotensive therapy. On cessation of CsA treatment, the mean serum creatinine concentration fell to the upper reference limit. The elevation of serum creatinine concentration was significantly higher in patients who either developed hypertension during Cyclosporin A therapy or who were previously known to be hypertensive. Patients with nephrotoxicity were significantly older than those in whom serum creatinine concentration remained within the reference range. Lithium clearance studies showed evidence of proximal renal tubular dysfunction which was partially reversible on dose reduction or withdrawal.