This is a retrospective analysis of marrow function in 171 recipients of an HLA-matched bone marrow transplant (BMT). Only patients with detectable hemopoiesis as indicated by leukocyte counts greater than 1.0 x 10(9)/l and platelet counts greater than 25 x 10(9)/l who were alive on day 30 were entered in the study. Poor marrow function was detected in 24 (14%) patients as indicated by a decrease in the peripheral blood counts to less than 40% of the maximal preceding values post-transplant in association with reduced marrow cellularity. Leukopenia (n = 4), thrombocytopenia (n = 3) or a combination of the two (n = 17) occurred 62 +/- 23 (SEM) days post-transplant and was associated with acute graft-versus-host disease (AGVHD) grade II or more and infection (n = 19) in the absence of clear rejection or persistence/recurrence of malignant disease. A multivariate analysis showed that AGVHD was the major risk factor (p = 0.001) for developing poor graft function. In the 24 patients with poor graft function, hemopoietic recovery was strongly associated with resolution of AGVHD and of infections. Their survival (27%) was the same as survival for other patients matched for GVHD who had no pancytopenia. The causes of death were GVHD (n = 13), pneumonia (n = 3) and infections (n = 1). This study draws attention to a particular type of poor graft function following allogeneic BMT that is characterized by (1) normal timing and quality of engraftment, (2) AGVHD of grade II or greater, (3) progressive and severe pancytopenia, and (4) multiple infections with poor clinical condition.(ABSTRACT TRUNCATED AT 250 WORDS)