Twelve patients with severe, painful diabetic neuropathy in the lower extremities were treated with imipramine and placebo in a fixed-dose, double-blind, crossover study of five plus five weeks. Seven patients experienced notable improvement while receiving imipramine and none while receiving placebo. The rating of specific symptoms at the end of each treatment period showed a beneficial effect of imipramine on pain, paresthesia, dysesthesia, numbness, and nocturnal aggravation. The plasma levels of imipramine and its metabolite desipramine were significantly higher in patients who benefited from imipramine treatment.