Abstract: Objective To understand the influence of storage time on quantitative detection of CD4+T lymphocyte with whole blood samples. Methods Twelve whole blood samples were collected from HIV-1 infected persons and stored at 4-8℃. The absolute numbers of CD4+ were detected every 24 hours from day 1 to day 6 after sampling with flow cytometer, four color fluorescence monoclonal antibody reagent and COULTER EPICS XL. The results were analyzed with SPSS 13.0 software. Results Compared with the quantitative detection result of CD4+ on sample collection day, the average number of CD4+ declined by 14.583/l 24 hours later, 22.083/l 48 hours later, 49/l 72 hours later, 53.417/l 96 hours later and 88/l 120 hours later. The difference on the detection results between the sample collection day and 24 hours later had no statistical significance (P=0.09), but the differences on other detection results had statistical significance (P0.05). Conclusion The detection result of CD4+ in blood samples (stored at 4-8℃) is reliable if the detection is completed within 24 hours or no more than 48 hours. The longer the samples are stored, the more CD4+T lymphocyte decline