This review is based on a lecture in which I was requested to present my personal experiences and views. Since its introduction into psychiatry more than 40 years ago, lithium treatment has in most countries gained wide acceptance in the prophylaxis of unipolar and bipolar affective disorders. At one time it was feared that lithium treatment might lead to a decrease in the glomerular filtration rate, but systematically collected data indicate that even long-term treatment does not induce renal insufficiency. During treatment, regular laboratory monitoring of serum lithium and creatinine concentrations is recommended. Recent studies suggest that long-term lithium treatment does not raise the mortality of manic-depressive patients and indeed may have a mortality-lowering and antisuicidal effect. Despite the availability of alternative therapies, lithium remains the treatment of choice for the prophylaxis of recurrent manic-depressive illness.