Molecular probes for cellular protooncogenes have recently been extensively used in order to search for functional and structural alterations in tumor tissues. Variable, and sometimes contradictory, results have been obtained regarding the frequency and clinical significance of amplification of the cmyc and cerbB‐2 protooncogenes in different series of human solid tumors. We addressed this question by performing Southern blotting analysis on 131 primary adult solid tumors of various tissues and 5 metastases of unknown origin, using molecular probes for both genes. Amplification of cmyc was found in 5 of the primary tumors, and amplification of cerbB‐2 in 5 others. In 2 tumors of the latter group, the cerbB‐2 gene was also rearranged. The distribution of these 10 tumors with regard to clinical stage and course of the disease did not point to an association between the amplification events and specific stage or prognosis. We concluded that, in this series, the amplification of both protooncogenes was occasional and was not a prognostic marker.