We evaluated a flow cytometric (FCM) two-color immunophenotyping of CD3+/CD4+ T-helper and CD3+/CD8+ T-suppressor lymphocytes in whole blood samples from HIV-infected individuals using monoclonal antibody reagents from three different manufacturers. Lymphocytes were firstly determined using CD45/CD14 in association with a forward scatter/side scatter gating strategy. CD3+/CD4+ and CD3+/CD8+ were then determined and compared. Reagents from all manufacturers showed good separation of lymphocytes, monocytes and granulocytes with high purity and recovery. There was a good correlation of the percentage of CD3+/CD4+ and CD3+/CD8+ lymphocytes amongst each of the manufacturer's reagents, but the fluorescent intensities of positive cells were not the same. This difference can result in poor discrimination of positive and negative non CD3 cells leading to erroneous results.