Normal tongue and cervical mucosa, premalignant cervical and vulvar lesions, primaries and metastases of squamous cell carcinomas from the oral, laryngeal, cervical and vulvar mucosa were analyzed for c-erbB2 and c-myc transcription with northern-blots using 32P single-stranded RNA probes. Transcription of c-erbB2 and c-myc could be detected for almost all tissues including normal samples. A slightly enhanced transcription level was found in three cervical intraepithelial neoplasias of Grade III (CIN III) but in none of the malignant lesions. Increased transcription of c-myc was observed in premalignancies and malignancies. It was more frequent in oral and laryngeal squamous cell carcinomas (SCC) (8 of 9 cases) than in genital SCC (3 of 11 cases) or premalignancies (3 CIS of 14 CIN/VIN). No relationships of c-myc enhanced transcription level with tumor grading and staging were noticed. Thus, mere oncogene expression is a widespread phenomenon in tissues of different histogenesis and quantitative analysis is necessary prior to ascribe any diagnostic or prognostic relevance. Moreover, the frequency of tumors with enhanced transcription may vary for phenotypically closely related tumors of different organs.