Cellular DNA content has been found to be an important prognostic factor in many human tumours, yet within the head and neck region few studies have examined its effect on survival and in those that have, findings differ. Eighty-one consecutive patients with squamous carcinoma of the tongue mainly treated by surgery and post-operative radiotherapy were studied. The DNA content of archival paraffin embedded tumours was measured by flow cytometry. Fifty-seven tumours were diploid and 24 were aneuploid. There was no association between ploidy status and age, sex, tumour size or nodal status. Ploidy status was not related to survival. These findings indicate that analysis of tumour DNA content in squamous carcinoma of the tongue does not provide any additional prognostic information for the individual patient.