Three species of salmonids, rainbow trout,Salmo gairdneri, brown trout,S. trutta, and marble trout, S.marmoratus, have been studied for their karyotypes. In rainbow trout 316 metaphases were studied and recorded 2nof 60 with 44 meta‐ to submetacentric and 16 subtelo‐ to telo‐centric chromosomes, and the number of chromosome arms (NF) of 104. Observation on 243 metaphases of brown trout showed 2nof 80 with 20 meta‐ to submetacentric, 60 telocentric chromosomes and thenfof 100. While in 164 metaphases from the marble trout 2nwas of the order of 80 out of which 22 were meta to submetacentric and 58 telocentric chromosomes withn