Expression of six cellular oncogenes in fresh human tumours and normal tissue from head and neck regions of 20 patients were assessed: 7 samples of normal tissue (controls), 4 premalignant (pleomorphic salivary adenoma) and 14 malignant tumours (squamous cell carcinoma) were examined. Normal and malignant tissue was available from the same patient in four cases, whereas normal and premalignant tissue in one case. Significant elevation of Ha-ras, Ki-ras, and myc oncogene expression were found both in premalignant and malignant tumours as compared to the normal tissue. Oncogenes fes, abl, and sis were expressed at similar low levels in all tissues examined. The results suggest activation of multiple oncogenes in premalignant and malignant tumours from the human head and neck regions.