The incidence of aplastic anemia appears to be relatively high in some parts of the world, including Pakistan. Since some of the etiological factors are shared by aplastic anemia and the preleukemic syndrome, there is a strong possibility that a proportion of cases of aplastic anemia may in fact be preleukemia. The study of chromosomes offers a relatively easy method of detecting cases of preleukemia, because some chromosomal abnormalities are frequently observed in this condition. Chromosomal studies were carried out in peripheral blood cell cultures of 31 patients with otherwise typical aplastic anemia. Chromosomal abnormalities were detected in 7 (22.5%) cases. The most common chromosomal abnormality detected was trisomy 8, seen in four cases. Other abnormalities detected were 22q-, t(14;22) and t(15;21), in one case each. These abnormalities have been found to be associated with AML, MDS, ALL, and NHL as well. We hypothesize that a proportion of cases of otherwise typical aplastic anemia may in fact be due to a leukemic process in evolution.