Functional studies of extracellular proteins are often performed using coimmunoprecipitation without purified proteins. However， in order to exclude unspecific reactions of contaminants and for quantitative analysis of specific functions， it is necessary to use purified proteins. It is usually very difficult， however， to purify sufficient amounts of reasonably pure extracellular matrix proteins from tissue samples， but the recombinant expression and purification of proteins in eukaryotic expression systems including insect cells and mammalian cells has proven an alternative powerful method. In this chapter， we describe the expression and purification of recombinant fibulins， but the methods can be also used for other extracellular proteins.