Using a mouse cDNA probe encoding for the major part of peripherin, a type III intermediate filament protein, we have assigned, by in situ hybridization, the mouse and human peripherin genes, Prph, to the E-F region of chromosome 15 and to the q12-q13 region of chromosome 12, respectively. These regions are known as homologous chromosomal segments containing other intermediate filament genes (keratins) and also other genes which could be co-ordinately regulated.