Glycosylation is one of the most common post-translational protein modifications. Carbohydrate-mediated interactions between cells and their environment are important in differentiation, embryogenesis, inflammation, cancer and metastasis and other processes. Humans and mice with mutations that prevent normal N-glycosylation show multi-systemic defects in embryogenesis, thereby proving that these molecules are essential for normal development; however, a large number of proteins undergo defective glycosylation in these human and mouse mutants, and it is therefore difficult to determine the precise molecular roles of specific N-glycans on individual proteins. We describe here a 'functional post-translational proteomics' approach that is designed to determine the role of N-glycans on individual glycoproteins in the development of Caenorhabditis elegans.