AbstractThe elderly are at high risk to develop neurotoxicity in the course of lithium therapy. This is especially true for patients with neurologic or cognitive impairments. This may occur even when lithium treatment is modified to include lower doses and lower target blood levels. The literature is reviewed concerning current uses of lithium in older patients. The rationale for expecting that red blood cell (RBC) lithium levels could have predictive value in the early detection of impending serious neurotoxicity is discussed. There appears to be a critical value for RBC lithium in the region of 0.6 mEq/ 1 that is ominous as a harbinger of impending toxicity. This critical concentration may be considerably lower for patients with dementia.