Since the generation of dendritic cells (DC) from myeloid precursor cells within the bone marrow (BM) was first reported, it has developed to one of the standard tools for studying DC biology in rodent systems. However, antigen-specific effects of such DC on polyclonal T cell populations may be influenced by the additional presentation of bystander antigens derived from fetal calf sera (FCS). This may lead to misinterpretations of the antigen-specific effects on the T cell response. In addition, many factors, including FCS, also influence the quantity and quality of BM-DC already during culture. Here, we review the factors that have an impact on the generation of BM-DC, including criteria regarding the mice, but also technical parameters and the different growth factors. The critical role of FCS in BM-DC cultures and alternative methods using murine sera or serum-free media are discussed. (c) 2007 Elsevier GmbH. All rights reserved.