The flow cytometer is capable of analyzing a large number of cells or cell nuclei. The flow cytometer has been used to analyze the DNA content of tumor cells from squamous cell carcinomas of the upper aerodigestive tract using a modification of the Vindelov staining procedure. The main difficulty in analyzing solid tumors using flow cytometry technology is the disaggregation of the cells and the quantification of the diploid point (2N point). A set of internal standards was developed for establishing the 2N point, as well as a technique for disaggregation, which is described. A histogram characteristic of a more aggressive squamous cell carcinoma which tends to recur more quickly and more frequently than the other squamous cell carcinoma histogram types was identified. The flow cytometer proved to be a practical method of analysis allowing for quantitative measurement of DNA content from a large number of cells originating from a squamous cell carcinoma. The trend between recurrence and histogram type will require further study.