We analysed the kinetics of haematological recovery after autologous bone marrow transplantation (ABMT) in 31 patients with non-Hodgkin's lymphoma, of whom 14 had received chemotherapy and 17 had received no chemotherapy before marrow harvesting. The time for recovery of polymorph (PMN) and platelet numbers was assessed in relation to patient's sex, age, the numbers of mononuclear cells (MNC) and of granulocyte-macrophage colony-forming cells (CFU-GM) reinfused, the therapy before harvesting and the conditioning regimens. The results showed that the most important factor influencing the speed of haematological recovery was therapy before marrow collection; recovery was faster in patients not treated before harvesting than in those treated. The mean day for PMN recovery to 0.5 x 10(9)/l was 14.6 vs 21.8 (p less than 0.001); the mean day for platelet recovery to 50 x 10(9)/l was 16.5 vs 44.4 (p less than 0.00002). The other parameters assessed did not correlate with the kinetics of haemopoietic recovery. We conclude that NHL patients who undergo ABMT without chemotherapy prior to marrow harvest have rapid haematological recovery, which suggests that better timing of the harvest could be of value in the management of NHL patients for whom 'reinforcement' with ABMT is scheduled.