The DNA index and proliferation rate (percentage of S-phase cells) of 52 head and neck tumours were analysed by flow cytometry. Thirty-one (60%) of these tumours were aneuploid, 21 (40%) diploid. The distribution of aneuploid tumours was nearly equal in all T-stages. In contrast, the number of aneuploid tumours increased with higher N-stages. Locoregional recurrences developed more often (69%) in aneuploid tumours than in diploid tumours (54%). Furthermore, recurrence presented earlier (median 5 months) than in the latter (median 11 months). Regional recurrences were mainly observed in aneuploid tumours, local recurrences in diploid tumours.