Studies performed in rabbit and mouse models and in a limited number of human subjects, show that transfused platelets bind thrombopoietin (TPO) and decrease its concentration in the circulation. The aim of the present study was to further examine this relationship. The material comprised 12 patients receiving a total of 21 transfusions, as part of the routine clinical treatment. Blood samples were collected from the patients immediately before and 30 min after completion of the platelet transfusion, and the corrected platelet count increment (CCI) was calculated. A commercially available ELISA kit was used to determine plasma TPO concentrations. Statistically significant reductions in median TPO concentration were observed in response to the platelet transfusions. Patients who were refractory to platelet transfusions showed the slightest decrease in TPO concentration. As for the linear regression between change in TPO level and CCI, only borderline significance was observed. Thus, our findings support the concept that platelets can remove TPO from the circulation.