Following testicular X-irradiation of Chinese hamster (Cricetulus griseus) males eight progeny (five males and three females) with reciprocal translocations (heterozygotes) were obtained. They were all phenotypically normal but semi-sterile. Homozygotes were produced successfully with CHAT3 (2p –;9q + ) and CHAT5 (2–;8q+). They were proven to be fertile. Thus, two homozygous stocks with distinct marker chromosomes were established. CHAT3 homozygotes have shown a high incidence of diabetes, while CHAT5 homozygotes had no genetic burden. Progeny tests of outcrosses and intercrosses with the heterozygotes and homozygotes were performed in both stocks. Karyological analysis of the first cleavage division showed the marker chromosomes of both stocks to be useful in distinguishing the paternal chromosome complements from the maternal ones.