The kinetics of marrow engraftment was retrospectively analysed in 55 patients with malignant lymphoma (ML) and 31 patients with acute lymphoblastic leukemia (ALL) after marrow-ablative therapy followed by autologous bone marrow transplantation. Thirty-eight percent of patients with ML, most of whom were transplanted in relapse and 13% of patients with ALL, mostly transplanted in remission, showed failed or delayed engraftment. Analysis of the total patient group showed that failure to recover platelet counts was significantly correlated with detection of disease in the marrow early after transplantation (p less than 0.001). Platelet recovery was also correlated with survival (p = 0.0001), disease-free survival (p = 0.0001), and the probability of relapse (p = 0.02). In those patients achieving engraftment, multivariate regression analysis failed to reveal any single in vitro test of marrow nucleated cell or progenitor cell numbers that significantly influenced time to achieve recovery of either granulocyte or platelet counts.