Seven cases of severe juvenile laryngeal papillomatosis were treated with exogenous leukocyte interferon (IFN-alpha). Tumor progression occurred in all cases before treatment. During treatment, the tumors decreased in size. When treatment was discontinued (five cases), tumor growth recurred, and after restarting therapy, the tumors once more decreased in size. In one case, the tumor completely vanished. In another case with extensive papillomatosis that extended up to the base of the tongue, a tracheostomy could be closed with only a thin mass of papillomatous tissue that remained on the vocal cords. Exogenous leukocyte interferon therapy can affect the clinical course of juvenile laryngeal papillomatosis. The optimal schedule for therapy has yet to be determined.