The debris from human bone marrow (BM) samples is generally filtered out and discarded prior to isolation of mesenchymal stem cells (MSCs). The purpose of this study is to develop a method to harvest MSCs from the debris and investigate their biological characteristics compared with the marrow counterparts. The BM tissue fragments were digested with collagenase and this treatment yielded mononuclear cells half to those from the corresponding filtered BM. The frequencies of colony-forming unit-fibroblast in these two cell populations were not significantly different. MSCs of two origins exhibited similar morphological and phenotypic features. Fluorescent dye-dilution assay showed that they grew at comparable rates both in the primary and passaging cultures. Further, they could be induced into osteoblasts, chondroblasts and adipocytes, as revealed by histological and molecular examinations. Thus, BM tissue fragments may serve as a new source of MSCs in the settings of bench experiments and clinical trials. (C) 2008 Elsevier Inc. All rights reserved.