Using DNA transfection analysis1 on NIH3T3 cells2, activated human oncogenes have been isolated from a variety of fresh solid tumours3. Thyroid neoplasias show a wide range of lesions varying from slowly progressive well-differentiated tumours to anaplastic highly malignant neoplasms4. Therefore they represent an attractive model to investigate the role of oncogene activation in different stages of the neoplastic state. Here we report the detection of transforming activity in DNAs extracted from five thyroid papillary carcinomas and two of their respective lymph-nodal metastases.