Cytogenetic analysis was performed on the metaphase spreads obtained from primary cultures of eight squamous cell carcinomas (SCCa) of the head and neck. Despite a variety of tumor sites and clinical stages, four of eight tumors studied showed the same interstitial deletion of a portion of the q arm of chromosome 7, i.e., del(7)(q22q34). In one tumor, this was the sole chromosome abnormality present. Three tumors showed multiple chromosome rearrangements, including deletion at 7q. Three tumors showed multiple rearrangements but did not have del(7q). One tumor had an apparently, normal karyotype. The implications for del(7q) as a primary chromosomal event in SCCa are discussed.