Flow Cytometric (FCM) DNA analysis was performed on surgical specimens taken from 17 patients with benign tumors and 26 with malignant tumors of the head and neck. The proportion of proliferative cells showing S, G2 and M phases in the DNA histogram was analyzed and correlated with the pathological findings. In malignant tumors, the “Proliferative Index (P. I.)” was significantly higher than in benign tumors, but in some specimens with malignant pathological findings, the P. I. was low. In such cases, the area occupied by tumor cells was very small. To interpret the cell kinetics of head and neck tumors with FCM correctly, one must take it into consideration that the tissue specimen obtained from the tumor may include both tumor cells and non-tumor cells.