We explain a protocol for straightforward isolation and culture of mesenchymal stem cells (MSCs) from mouse bone marrow (BM) to supply researchers with a method that can be applied in cell biology and tissue engineering with minimal requirements. Our protocol is mainly on the basis of the frequent medium change in primary culture and diminishing the trypsinization time. Mouse mesenchymal stem cells are generally isolated from an aspirate of BM harvested from the tibia and femoral marrow compartments, then cultured in a medium with Dulbecco's modified Eagle's medium (DMEM) and fetal bovine serum (FBS) for 3 h in a 37 degrees C-5% CO(2) incubator. Nonadherent cells are removed carefully after 3 h and fresh medium is replaced. When primary cultures become almost confluent, the culture is treated with 0.5 ml of 0.25% trypsin containing 0.02% ethylenediaminetetraacetic acid for 2 min at room temperature (25 degrees C). A purified population of MSCs can be obtained 3 weeks after the initiation of culture.