Allopurinol was used in the treatment of 10 patients with kala-azar. Of six patients who had previously failed to respond satisfactorily to Pentostam, "cures" were achieved in four. However, it was necessary to add Pentostam to the allopurinol in one, and another relapsed after apparent "cure" but again responded to allopurinol. The response of four patients who had had no previous treatment for kala-azar was less satisfactory.