OBJECTIVES: Study the renal consequences of lithium therapy and find out whether lithium-induced chronic renal toxicity can provoke a progressive nephropathy, leading to advanced renal failure, requiring periodical dialysis. METHODS: Fifty-three patients treated with long-term lithium salts were included in the study. They had developed chronic renal failure (creatinine clearance inferior to 80 ml/min) not due to any other cause. RESULTS: These patients had received lithium salts for a mean period of 17.7 years. The mean reduction in creatinine clearance was of 2.23 ml/min/year. Final clearance correlated negatively with the duration of lithium administration. In 7 patients treated a mean of 22 years, progression towards terminal kidney failure required periodical dialysis. Around 30% of patients exhibited mild hypercalcemia. CONCLUSION: Lithium nephropathy inducing progressive renal failure is a reality. Its prevalence in patients treated long-term with lithium should be assessed.