Toxicity related to autologous PBSC infusion is well known and traditionally attributed to the presence of DMSO as cryoprotectant. But despite DMSO depletion, adverse events continue appearing. We have conducted a retrospective study to determine the incidence of adverse events related to the PBSC infusion in a large series of 144 patients. Adverse effects were observed in 67.36% of patients, although most of them were of grade 1 or 2. The adverse events most frequently reported were allergic reactions, followed by general, gastrointestinal and respiratory symptoms. In the univariate analysis, age (P=0.01), the volume infused (P=0.005), the amount of DMSO (P=0.008), the total nucleated cells (P=0.002), the total number of granulocytes (P=0.000001) and clumping (P=0.000001) were associated with the occurrence of adverse events. In the multivariate analysis, two protective factors, age (P=0.05) and sex (P=0.004), and two risk factors, the number of granulocytes, with a relative risk of 1.18 (95% confidence interval, 1.06-1.31) (P=0.002), and clumping, with an relative risk of 1.94 (95% confidence interval, 1.15-3.29) (P=0.013), were identified. The best cutoff point for the prediction of the occurrence of adverse events, with a sensitivity of 47% and specificity of 89%, was 6.065 x 10(9) granulocytes.