By in situ hybridization we show that the SS rRNA genes in the mink map to chromosome 2q in three loci. The 2q1.1 locus containing 34% of the 5S rDNA, maps close to the centromere, and the remaining two loci of the 5S rDNA map to 2q1.3 (52%) and to 2q2.3. (14%). These data were obtained with a tritiated transcript of the 5S rRNA gene containing 121 bp. In a comparative FISH study performed with a biotinylated transcript of the 5S rRNA gene the procedure failed to detect the 2q2.3 site. A closely corresponding difference between the two procedures experienced previously in man and in the crab-eating macaque is discussed. The present results suggest a homology between 2q in the mink and part of 1q in man harbouring the 5S rRNA genes in 1q42.13 and 1q31, respectively.