Retrospective analysis of 80 patients with aplastic anaemia (AA) was performed in order to examine clonogenic properties of granulomonocytopoiesis precursors and to specify the extent of disorder of hemopoiesis in AA. Sharp decrease of clonogenic properties of precursors, especially in severe form of AA was established to be present in 95% of patients, while only in 5% of patients initial indexes of the clonogenic ability were discovered to be normal. After treatment with ALG, prednisolum and androgen and also after splenectomy, clonogenic ability increased appropriately in 43%, 16.6% and 76.9% of patients, although the effect was not steady. The best results were obtained after allogenic transplantation of bone marrow (TBM), when the clonogenic properties normalization was observed against the background of remission 1-3 years lasted. Thus, low indexes of clonogenic properties of the precursors of granulomonocytopoiesis in AA, and positive effect of TBM may indicate the lesion of the precursor. At the same time normal initial indexes in some patients, and diverse effect of different methods of therapy make it possible to admit the probability of the lesion of stromal microenvironment cells.