The primary goal of the proposed study is to examine the utility of a new imaging study, Positron Emission Tomography with F-18 Fluorothymidine (FLT PET), in the early treatment evaluation of head and neck cancer. FLT uptake in the tumor correlates with the rate of cell proliferation. It is therefore hoped that changes in tumor FLT uptake after therapy will reflect change in the number of actively dividing tumor cells and will provide early assessment of treatment response.