OBJECTIVE Thrombocytopenia occurs in pediatric patients after SCT and has to be treated with platelet transfusions which bear certain risks and represent a significant cost factor. Monitoring immature platelet (IPF) fraction has been proposed to predict platelet recovery thereby reducing the need for transfusions. METHODS Hematological parameters including IPF were systematically studied in 17 pediatric patients after either peripheral blood or bone marrow stem cell transplantation. RESULTS Time to platelet recovery depended on the source of stem cells while no differences were detected between percentaged IPF peak concentration and time between IPF peak concentration and platelet recovery between the groups. Correlation between the timepoints of percentaged IPF peak and platelet recovery was high but large interindividual differences were observed concerning the duration of this period. In addition, in some patients high IPF concentrations were not followed by platelet recovery. CONCLUSIONS Although in general high IPF concentrations are followed by platelet recovery wide interindividual variations exist and even no recovery was recorded in four patients. As the latter children are not readily identifiable beforehand IPF should not be used to omit platelet transfusions.