We sought to establish the prevalence of lithium-induced end-stage renal disease in two regions of Sweden with 2.7 million inhabitants corresponding to about 30% of the Swedish population. Eighteen patients with lithium-induced end-stage renal disease were identified among the 3369 patients in the general lithium-treated population, representing a sixfold increase in prevalence compared with the general population for renal replacement therapy. All lithium-treated patients were older than 46 years at end-stage renal disease with a mean lithium treatment time of 23 years with ten patients having discontinued lithium treatment an average of 10 years before the start of renal replacement therapy. The prevalence of chronic kidney disease (defined as plasma creatinine over 150 micromol/l) in the general lithium-treated population was about 1.2% (excluding patients on renal replacement therapy). Compared with lithium-treated patients without renal failure, those with chronic kidney disease were older and most were men but, as groups, their mean serum lithium levels and psychiatric diagnoses did not differ. We found that end-stage renal disease is an uncommon but not rare consequence of long-term lithium treatment and is more prevalent than previously thought. Time on lithium was the only identified risk factor in this study, suggesting that regular monitoring of renal function in these patients is mandatory.