Intralesional injection of beta-interferon can lead to remission of metastatic melanomas. Simultaneous radiotherapy may augment the effect of these injections. The effect of intralesional beta-interferon injections combined with radiotherapy was examined in patients with metastatic malignant melanoma. A total of 20 patients with inoperable, incapacitating and disfiguring malignant melanoma metastases were treated with simultaneous external beam radiotherapy (electrons and/or photons) and intralesional injection of beta-interferon. The total radiation dosage ranged from 40-50 Gy, fractionated as 1.8 Gy five times per week. beta-Interferon (Fiblaferon) 3-5 million units per injection was administered three times weekly until symptoms disappeared or until termination of therapy. One patient was treated with beta-interferon alone; the area harbouring the tumour had been previously irradiated. Five patients treated in this way showed partial remission after combined therapy and 12 showed complete remission, with permanent regression of metastases. The latter group included five patients with lengthy survival times, including one patient who has been free of symptoms for 7 years following treatment. Injected metastases showed complete regression in the patient who was treated exclusively with beta-interferon post-irradiation. In conclusion, combined treatment with radiotherapy and intratumoral injection of beta-interferon controlled local tumour growth in inoperable metastatic malignant melanomas.