 Our pilot study using cellular DNA cDNA microarrays to examine the buccal mucosa of smokers and non-smokers demonstrated that smokers could be separated from non-smokers based solely on the patterns of gene expression observed. We were able to identify 924 genes whose expression differs significantly between samples from smokers and non-smokers. Several genes were also shown to be either up or down regulated in our earlier research applying microarray analysis to head and neck cancer tumors. Many of these represent genes of possible interest as early molecular markers for head and neck carcinogenesis. 