Psoriasin is a low molecular weight protein of the S100 family, which is highly upregulated in psoriatic epidermis, and whose function is related to skin inflammatory responses. We have applied a cDNA probe from the corresponding psoriasin gene S100A7 in a refined localisation analysis. S100A7 was mapped physically by human/rodent somatic cell hybrid analysis, and more precisely genetically by multilocus linkage analysis of 40 CEPH (Centre d'Etude du Polymorphisme Humain) families. The resulting 12-point linkage map was supported by odds of at least 1000:1, where S100A7 could be placed with a multipoint lodscore of 27.4 in an approximately 7-cM interval. The order of the 12 loci was as follows (with the best estimates of recombination frequencies given in between): AMY2B-0.091-D1S73(0.039)-D1S11(-0.053)-D1S189(-0 .017)-D1S1252 (-0.017)-D1S13(-0.078)-D1Z5(-0.051)-S100A7(-0.022)- MUC1(-0.026)-SPTA1 (-0.066)-ATP1A2(-0.014)-APOA2. Furthermore, from this map S100A7 could be assigned to the regional position of chromosome 1cen-q21. The linkage information presented should be of great value in association and linkage studies of diseases where psoriasin, or some of the several other very closely linked and functionally related genes, are seen as candidate genes, e.g. in psoriasis.