According to the cellularity in the first bone marrow aspirate, 541 cases of aplastic anemia (AA) diagnosed in the Peking Union Medical College Hospital were divided into two groups--hypoplastic and hyperplastic. Comparison of the transformation, remission and long-term survival rates in the two groups showed the following results. (1) Transformation: In the hypoplastic group, 60% of the cases maintained the original degree of proliferation, 34% was transformed to hyperplastic, 3% had repeated transformation and 3% became leukemic. In the hyperplastic group, 44% maintained the original degree of proliferation, 44% was transformed to hypoplastic, 9.3% had repeated transformation and 2.7% became leukemic. (2) Remission rate: The total remission rate was 15.9% in the hypoplastic and 14.6% in the hyperplastic group. (3) Long-term survival rate: The 1-, 5- and 10-year survival rates were 70.43%, 57.66% and 51.51% in the hypoplastic group, while they were 86.7%, 71.24% and 63.34% respectively in the hyperplastic with statistical significance (P less than 0.01). It is emphasized that AA can not be ruled out if there is hyperplasia in the bone marrow smear taken for the first time or in several smears taken from the same site. Smears taken periodically from different sites are essential for correct diagnosis.