This investigation was performed to evaluate the influence of the static magnetic field up to 15 mT on the viability and proliferation rate of rat bone marrow stem cells. Cells from passage 5 were trypsinized, and a cell suspension was prepared. The cells were counted and cultured in 25-cm(2) flasks. They were incubated for 1 d, washed with phosphate-buffered saline, and then exposed with different intensities of static magnetic field (4, 7, and 15 mT) at different exposure times (24, 48, 72, and 96 h). Cells were then washed with phosphate-buffered saline, trypsinized, and a cell suspension was prepared separately from each flask. To investigate the viability and proliferation rates of treated cells, staining with Trypan blue and counting were performed with an optical microscope. The mean number of whole cells and living cells was considered as proliferation and survival rates, respectively. Increasing of intensity and time of static magnetic field exposure decreased the viability percent and proliferation rate in treated groups compared with corresponded control. However, reduced cell viability, where this occurred, is exclusively due to apoptosis since necrosis is never observed by others.