Peripheral blood stem cells (PBSC) could contribute to tissue regeneration through the ability to form somatic cells. CD34 positivity is regarded as stem cell (SC) or endothelial progenitor cell (EP) marker. According to literature natural substances could increase the release of CD34 positive (CD34+) cells. In this study we investigated the basic rate of CD34+ cells in peripheral blood of CBA/Ca (H-2k haplotype) and BALB/c inbred mice by flow cytometry. Then we treated the mice with a new mixture of medical herbs, and we measured the level of CD34+ cells at 1, 3, 6, 18 and 24 hours after the treatment. A biological rhythm in the untreated blood was detected. Moreover the used herbal compounds increased the number of CD34+ cells.Although SC number is individually and highly variable in peripheral blood, the fluctuation could be used as a biomarker like the other compounds of peripheral blood in different aspects in risk assessment.