Dermal fibroblasts (DF) possess chondrogenic differentiation potential but whether DF, or a subpopulation of DF, can form a typical cartilage structure in culture is unknown. In this study, human DF were co-cultured with porcine articular chondrocytes on a biodegradable scaffold of polylactic acid/polyglycolic acid. Histological analysis demonstrated that some DFs can be induced to form cartilage lacuna structure showing the existence of a chondrogenic subpopulation of human DF. Moreover, the 3D-co-culture system can serve as an optimal model for directing stem cell differentiation in vitro.