Short-term cultures from five squamous cell carcinomas of the larynx were subjected to cytogenetic analysis. In the first three cases, two, three, and 10 chromosomally abnormal clones were detected. Single clonal abnormalities were found in cases 4 and 5. In addition to the clonal aberrations, a number of nonclonal changes were also present in all five tumors. None of the aberrations, clonal or nonclonal, was found in more than one tumor, nor did the rearrangements correspond to any of the consistently cancer-associated aberrations known from other tumors. The remarkably diverse karyotypic picture of the five squamous cell larynx carcinomas, in particular the finding of cytogenetically unrelated clones in three of them, suggests that some of these neoplasms are polyclonal rather than monoclonal.