Objective To evaluate the application values of two kinds of single-platform flow cytometric methods,the Volumetric method based on flow sensor and the Trucount method based on Trucount beads,in the counts of T-lymphocyte subsets in peripheral blood of patients after transplantation.Methods The absolute number and percentage of CD4 +,CD8 +,and CD3 + T cells in peripheral blood samples from 107 patients after liver or renal transplantation were determined by the Trucount method and the Volumetric method,respectively,and their results were compared using paired t-test and linear regression analysis.Five samples with low CD3 + counts were selected and the precisions of the absolute number of CD4 +,CD8 + and CD3 + T ceils detected by the Volumetric method were evaluated.Results There was no significant difference in the levels of CD4+,CD4+/CD3+,CD8+,CD8+/CD3+,and CD4+/CD8 + in peripheral blood between the Trucount method and the Volumetric method (P ＞ 0.05),and the linear regression coefficients between them were from 0.9 to 1.1.When the concentration of CD3 + was equal or more than 40/μL,the coefficients of variation (CVs) were below 5.5％ for the Volumetric method.When the concentration of CD3 + was 20/μL,the CVs of CD3 +,CD4 +,and CD8 + were 5.19％,10.28％ and 6.48％,respectively.Conclusion The single-platform method based on flow sensor is accurate and reproducible for counting T-lymphocyte subsets in peripheral blood,which may be used to monitor the immune state of the patients after liver or renal transplantation.