We investigated surface immunophenotypes of peripheral blood mononuclear cells (PBMC) collected by cytotoxic and cytotoxic/G-CSF mobilization of peripheral blood stem cells (PBSC) from 38 patients with haematological malignancies in complete remission who underwent consolidation chemotherapy. PBMC were collected by leucapheresis during the haematopoietic recovery phase after intensive chemotherapy. G-CSF was used for mobilization of PBSC in 19 cases. Surface immunophenotyping of frozen-thawed PBMC was performed by flow cytometry. Our findings showed that monocytes and T cells were the two major cell components of PBMC. There were very few B cells in PBMC. Expression of CD45RO and HLA-DR was elevated in lymphocytes, suggesting that T cells in PBMC were activated. The percentage of CD34 positive cells were significantly increased in PBMC collected by cytotoxic/G-CSF mobilization (group 1) compared with PBMC collected by cytotoxic mobilization (group 2). There were significantly higher percentages of CD14 and CD33 positive cells in group 1 than in group 2. The percentage of CD4 positive lymphocytes positive for HLA-DR was significantly higher in group 1 compared with group 2. These observations indicated that PBMC contained a large number of monocytes and activated T cells, especially in cytotoxic/G-CSF mobilization.