A novel 160-kDa intermediate filament associated protein, named restin (Reed-Sternberg intermediate filament associated protein), is specifically expressed in the malignant cells of Hodgkin’s disease and anaplastic large cell lym-phoma (Ki-1 lymphoma). The combination of chromosomal R-banding and fluorescence in situ hybridization (FISH) with the use of two fluorescent dyes, fiuorescein isothiocyanate and propidium iodide, allowed simultaneous detection of the hybridized DNA sequence and chromosomal R-banding. By this technique, the gene coding for restin (RSN) was assigned to chromosome region 12q24.31→q24.33, while localization of the α-2-macroglobulin receptor (A2MR) was refined to 12q13.1→q13.3. To further analyze the restin gene, a 500-kb YAC clone containing the gene was isolated and analyzed. A restriction map of this area is presented.