Arabinogalactanproteins (AGPs) are proteoglycans of the extracellular matrix o f most plants. Since the late 1980s, AGPs have attracted widespread attention from plant biologists following reports of their involvement in plant development. In particular, the use of monoclonal antibodies to carbohydrate epitopes of AGPs has demonstrated stage- and tissue-specificity and has led to suggestions that they are involved in tissue morphogenesis. The recent cloning of the genes for several AGP protein backbones allows us to consider new strategies to address their function. Here, we summarize our knowledge of AGPs and consider parallels with animal proteoglycans as a possible framework for future work.