Since the discovery of a viral aetiology (HPV 6 and 11), alpha-interferon (alpha-IFN) following surgical procedures has proved effective. In this article, we report on nine patients (four children, five adults) with laryngotracheal papillomatosis who received interstitial alpha-2a-IFN injections (Roferon, 3 Mio. IU) into the laser surgical coagulation area following laser excision of papilloma. The average duration of treatment is 29 months (Table 3). In all cases IFN therapy proved to respond with no initial failure. In five cases the treatment was finished after a four-year period with no signs of tumour recurrence (Table 4). One patient (N., P. in Table 4) with excessive manifestations spread over pharynx, larynx and trachea achieved partial remission with definite control over the disease for (so far) 17 months. Two patients have remained free of disease for five and seven months (J., D. in Table 4 and Fig. 1 a-c) after initial therapy onset with complete remission. Another child (W., F. in Table 4) had a recurrence after complete remission for ten months and no observation period for eight months. After recurrent IFN-application this patient has been tumour-free for now six months. Apart from flu-like symptoms no side effects of intralesional IFN-injections could be seen. The obtained results confirm that combined laser surgery and alpha-IFN treatment is the therapy of choice up to now. Since IFN is not a benign agent and systemic administration bears potential side effects, adjuvant intralesional alpha-IFN is effective and safe and extends the therapeutical possibilities available in laryngotracheal papillomatosis.