Abstract : Clustered, Regularly Interspaced Short Palindromic Repeat (CRISPR) system is a putative RNA-interference-based immune system conferring an acquired resistance against foreign DNA agressions in prokaryotes. It consists of a succession of highly conserved regions (DR) varying in size from 23 to 47 bp, separated by similarly sized unique sequences (spacer) of usually viral origin. Polymorphism can be observed in different strains of a species and may be used for genotyping. This thesis describes three bioinformatics tools available freely on the web (http://crispr.u-psud.fr) and their applications for the CRISPR investigations and typing. The first one is CRISPRFinder, a tool that allows the identification of CRISPRs from published genomes. The second one is CRISPRdb, a database of CRISPRs in the sequenced prokaryotes and several associated tools to facilitate its query and the CRISPRs investigations. The third tool is CRISPRcompar for the identification and comparison of CRISPRs loci and their component determination.