We investigated the efficacy of amitriptyline in seven patients with pathological laughing caused by cerebrovascular diseases. In a double-blind placebo-controlled cross-over trial comparing amitriptyline with placebo, 5 of these 7 patients were judged to have shown improvement with amitriptyline, and 1 patient improved with placebo. This difference was statistically significant. No significant side effect of amitriptyline was observed. There was no significant change between amitriptyline and placebo in both self-rating depression scale and minimental state test score. These results suggested that amitriptyline was useful in treating pathological laughing.