Glycine-rich proteins (GRPs) containing more than 60% glycine have been found in different tissues from many eukaryotic species. Despite the availability of literature on different groups of GRPs, there are few reports in which they are all considered and compared together. Some of these proteins are components of the cell walls of many higher plants. In most cases, it has been shown that they are accumulated in the vascular tissues and that their synthesis is part of the plant's defense mechanism. Other distinct types of GRPs are characterized by having structures and functions similar to animal cytokeratins or by a domain with typical RNA-binding motifs. The availability of cloned GRP genes facilitates the study of the function of this diverse class of proteins, which is expected to enhance the understanding of cell physiology.