This study was designed to ascertain whether a prior reduction of tumor size by drugs could affect the final outcome of tumors treated with radiation. 142 patients with head and neck cancer (oropharynx, maxillary antrum and intra-oral) were randomized for the study. In 72 cases, irradiation was preceded by a continuous intra-arterial infusion of 3-5 mg/day methotrexate to a total dose of 90-120 mg; the other 70 patients were treated with radiotherapy alone. Chemotherapy, given prior to radiotherapy, caused a shift in the tumor stage (i.e. a reduction in tumor size) in more than one third of the cases. The overall 5-year survival was 43% in the combined treatment group and 25% in the group treated with radiation alone (statistical difference: p less than .05). However, when analysed separately the difference was statistically significant only in oral cavity tumors (5-year survival of 54% in the combined modality group vs. 27% in the control group), although local control rates after both single and combined modalities were not statistically different from those of oropharynx and maxillary antrum tumors. In these last lesions, however, the dissemination of disease was more frequent; therefore, the lack of improvement of cure rate with the combined modality in these cases seems to be related to both the higher tendency of these tumors to disseminate and the low effectiveness of intra-arterial chemotherapy in controlling distant metastases. Mild and transient local and systemic toxicities were observed during chemotherapy infusion, but no radiosensitising effect on normal skin and mucosa was seen during radiotherapy in patients who had received pre-irradiation chemotherapy.