During malignant transformation, cells accumulate genetic and epigenetic alterations. Since ten years, the knowledge of the whole human genome, associated with the development of new molecular biology techniques allowing global analysis, encouraged the identification of these anomalies. Thus, transcriptome studies with DNA chips allowed the characterization of genes groups whose expressions vary according to the type of tumors or according to their recurrence. We analysed adrenal tumors with DNA chips and tried to characterize recurring carcinomas. On the other hand, tumor suppressor genes expression could be inhibited by epigenetic modifications like gene promoter hypermethylation. With development of sensitive methods like PCR, methylation profile could be defined. We were interested in lung and head and neck tumors and tried to evaluate if the presence of methylated gene in bronchial lavage or in saliva could be a good marker for the early detection of a primary tumor or of a recurrence.