Fluorescence in situ hybridization has been used in a cytogenetic analysis to map 15 cosmids on human chromosome 22. Thirteen cosmids were localized on the long arm of chromosome 22 (22q) while two other probes displayed a hybridization signal on 22p and the short arm of the acrocentric chromosomes of groups D and G. The regional assignment of these new chromosome markers will improve the mapping of chromosome 22; they can be used to detect numerical and structural aberrations of this chromosome involved in numerous pathologies.