Hematopoietic reconstitution has been studied in 180 patients after autologous bone marrow transplantation based on peripheral blood cell (PBC) recovery time and marrow progenitor counts sequentially tested for up to 4 years. Several factors that could influence hematopoietic reconstitution have been analyzed including sex, age, diagnosis, disease status, conditioning regimen, graft progenitor content, graft in vitro purging, and postgrafting administration of growth factors. Before transplantation, marrow progenitor values were normal only for colony-forming unit granulocyte macrophage (CFU-GM) in contrast to colony-forming unit-erythroid (CFU-E), burst-forming unit-erythroid (BFU-E), and colony-forming unit-megakaryocyte (CFU-Meg). After transplantation, as described with allogenic grafts, these values remained low for several years, although PBC counts were nearly normalized within a few weeks. Pregraft values were reached after 2 years for CFU-GM and BFU-E, and after 4 years for CFU-E, while CFU-Meg failed to reach pregraft values after this time. Normal levels were reached after 4 years only by CFU-GM. On univariate and multivariate analysis, the following factors appeared to delay both PBC and marrow progenitor reconstitution: underlying disease (particularly acute myeloid leukemias), graft characteristics such as low stem cell content and in vitro purging, conditioning regimens with total body irradiation or busulfan, and lack of postgraft administration of growth factors. In conclusion, high-dose therapy followed by bone marrow transplantation induces a deep and prolonged impairment of hematopoiesis irrespective of any alloimmune reaction or postgraft immunosuppressive therapy.(ABSTRACT TRUNCATED AT 250 WORDS)