Survival in acute leukaemia depends on the achievement of complete remission (CR). However, CR is not a clear-cut phenomenon and certain variables of its definition could more accurately characterize the quality of the remission. Because platelet recovery > 100 x 10(9)/l is an essential component of CR in acute leukaemia, we hypothesized that time to platelet recovery (TPR) might be predictive of overall survival (OS) or disease-free survival (DFS) in acute lymphoblastic leukaemia (ALL). We analysed TPR in 249 patients with ALL who entered CR after one course of induction chemotherapy and correlated TPR with DFS and OS. TPR was significantly associated with both DFS and OS if it occurred within a maximum of about 60 d from start of therapy. Furthermore, during that time period, the relative risk of death increased with increasing TPR. Although presence of the Philadelphia chromosome was the single most important adverse feature at diagnosis, the effect of TPR on survival continued to be significant within this patient subgroup. This effect was so pronounced that Philadelphia chromosome-positive patients with a TPR of 12 d had a better outcome than Philadelphia chromosome-negative patients with a TPR of 48 d. Thus, a short TPR seems to be able to override adverse characteristics in the outcome of ALL patients treated with chemotherapy. We conclude that a quicker TPR predicts longer DFS and OS in patients with ALL. As platelet counts are obtained almost daily in patients undergoing chemotherapy, TPR can readily be utilized to assess the prognosis of these patients.