PURPOSE: DNA chip is a recently developed technique allowing analysis of thousands of genes at the same time in multiple biological samples. In few years it has become an obligatory step in massive gene expression study. The enormous quantity of results generated and the new way of thinking allowed make this kind of study a true revolution. KEY MESSAGE AND RECENT FACTS: The enormous discovery potential permitted by the accomplishment of multiple genomes sequencing and the advent of technologies allowing massive gene expression analyses have totally modified the diseases approach. Considering the obtainment of a real full picture of the transcriptional activity in an organ, tissue or cell is now legitimate. DNA microarray is obviously not the only technique allowing such type of analysis but it is without contest the technology which is the most popular and the one which has been recently the subject of the most important developments. It is certainly the technology which brought the main advances in tumour classification and discovery of new biomarkers. The first results based on this technology in inflammatory diseases have recently been reported. PERSPECTIVE AND PROJECTS: The optimal use of DNA microarrays will necessitate a powerful statistical analysis and an high quality biological experimentation. Strict standard and quality criteria are developing. Obviously, the DNA chips have a role to play in multifactorial inflammatory diseases mainly through their potential to bring new answers to diagnostic and pathophysiological problems. One potential development of the technique in such diseases will be the definition of disease specific gene profiles and the generation of chips allowing the detection of few targeted genes with all the known mutations of these genes. The correlation of global or targeted gene expression with clinical and pathological data will allow a new step forward in the understanding and taking care of inflammatory diseases.