The accuracy of three automated haematology analysers [Sysmex XE-2100 (both optical and impedance mode), Bayer Advia 120, and Beckman Coulter LH-750] was compared with the immunoplatelet reference method for platelet measurement. A total of 165 blood specimens were obtained from patients and platelet counts were determined using the four-automated haematology analyser methods and the immunoplatelet reference method. The coefficients of determination (R(2)) between the automated haematology analyser methods and the immunoplatelet reference method for the overall platelet range were >0.98. A bias study, however, showed some disagreement. The use of a coincidence correction calculation for the immunoplatelet method did not improve the correlation between the immunoplatelet method and the automated haematology analyser methods. To estimate the possibility of inadequate platelet transfusion, the number of prophylactic platelet transfusion indications determined by the automated haematology analyser platelet counts were compared with the number of transfusion indications according to the platelet counts determined by the immunoplatelet method. An additional 48 blood specimens were included in this analysis. All of the automated haematology analysers showed some disagreement in the transfusion indications when compared with the immunoplatelet method, suggesting the possibility of inadequate platelet transfusion.