A variety of in vitro study methods have been used to elucidate the roles of matrix molecules in biomineralization processes. Among these, gel diffusion-precipitation studies have proved to be an effective tool. This methodology is uniquely capable of characterizing the effects of matrix molecules on mineralization while only using very small quantities of material. Furthermore, gel methods have been extended for use as a mineralization assay system to characterize modified matrix molecules and synthetic analogues. Here we discuss the advantages and limitations of gelatin, agar, agarose, and other systems for studying the mechanisms of biomineralization.