Lithium chloride at two different doses (1 mEq/kg and 2 mEq/kg) IP BID for 10 days failed to inhibit muricidal behavior in rats. Lithium chloride at the higher dose caused neurotoxicity in 6 of 11 rats as measured by the rotorod. These dosages generated serum levels of 0.70 and 1.00 mEq/L respectively. The same behavior was blocked by imipramine HC1 at an ED50 of 8.5 mg/kg 45 min following a single IP injection without evidence of neurotoxicity by the rotorod method. These results indicate that lithium chloride is unlike the tricyclic agents in the muricide test. Therefore, if its clinical antidepressant activity is substantial, it may be most effective in a neurochemically different class of depressives than the tricyclics.