Chromosomal studies were carried out on peripheral blood leukocytes of sixty-five cases of rubella potients, and an increased frequency of chromosome breakages was observed. These abnormal chromosomes were mostly simple breakages such as chromatid or isochromatid breaks, gap and fragments. These was distributed at random in all chromosome groups, but showed a higher frequency in Groups, A, B and C and were higher during the acute phase of the disease. The fact that chromosomal aberrations were found in rubella patients, stimulates us to study the relationship between rubella virus and its teratogenesis.