Background and objectives: Multiple transfusions can induce immunomodulation. This study was carried out to investigate the immunological status of 50 transfusion-dependent children with ß-thalassaemia, taking into account that lymphocyte characteristics are affected by sex, age and race. We paid particular attention to the influence of transfusion and serum ferritin on the lymphocyte subsets which may be affected by the exposure to foreign antigens. Materials and methods: By multicolour immunofluorescent analysis using flow cytometry, we determined lymphocyte characteristics with regard to major subsets (T lymphocytes, B lymphocytes and NK cells), activation (membrane IL-2 receptor CD25, HLA-D) and memory/naive T cells (CD45RO/CD45RA). Data from 51 age- and sex-balanced children served as controls. Results: The normal Chinese children had higher NK levels than the ß-thalassaemia children. The levels of CD25 and HLA-D indicated a broad-based increase in activation status. Memory T cells were also increased when compared with their normal counterparts. We found additional and more marked alterations in the lymphocyte subsets of those who had received over 100 transfusions. While levels of NK cells were inversely correlated with the number of transfusions, CD25+ cells increased with transfusions. Conclusion: Many multitransfused ß-thalassaemia children have altered levels of lymphocyte subsets compared with normals. What remains to be investigated is the long-term consequence of possessing low NK and non-MHC-restricted T cells (CD3+CD56+CD16+) and a high activation status in terms of resistance of infections and development of malignancy.