During the last 10 years, several reports have suggested that abnormalities in DNA content may be associated with clinical course in hematological and solid neoplasias. Measurement of this parameter by flow cytometry, especially when supplemented with additional cellular markers, has been indicated as a valuable prognostic tool in several human cancers. We recently addressed further these points in a prospective study on squamous cells cancers of the head and neck region (HNSCC). In these tumours, cell cycle kinetics and DNA ploidy may add prognostic information and can also provide a rationale for improving the results of radio (RT) or chemotherapy (CT). We used the in vivo incorporation of bromodeoxyuridine (BUDR) coupled with bivariate (DNA/BUDR) flow cytometry in a series of 232 patients (median age 62 yrs, range 45-74; 60 larynx, 45 oral cavity, 63 oropharynx and 64 nasopharynx) in different clinical stages (40 SI, 64 SII, 68 SIII, 60 SIV). 134/232 (57.7%) of patients were aneuploid with a median DNA index of the aneuploid peak of 1.4 (range 1.2-2.2). Median values of BUDR-labelling index (LI) DNA synthesis time (Ts) and potential doubling time (Tpot) were : 8.9% (2-17.6), 11.5 hrs (5-28) and 5.5 days (2-30), respectively. DNA ploidy and BUDR-LI were not significantly correlated with tumor site, clinical stage or pathological grading but DNA-aneuploid tumors showed shorter Tpot (4.1 days) than DNA-diploid ones (8 days) (p<.05). An analysis of the predictive power of biological and clinical factors with respect to both the tumor response and the relapse-free interval in two groups of SIII-SIV patients (74 patients treated with RT and 85 patients treated with RT +DDP / 5-FU- based CT) showed a statistical significance only for the lymphonodal status (p<.0005 and p<.005) followed by the Tpot (p<.0005 and p<.05). As a general conclusion, these results should be considered in designing kinetically- based clinical trails for HNSCC.