Studies of glycoconjugates are now entering an era when their functional analysis in tissues is of primary importance. This information is vital for determining how these molecules contribute to disease, and how we might manipulate them to improve human health. Insights into glycoconjugate function are coming in some large measure from studies of the fruitfly Drosophila melanogaster. The complement of Drosophila glycoconjugates, their conservation with vertebrate glycans, together with the vast array of molecular and genetic tools available for studying this animal, make Drosophila a very powerful model organism for understanding the function of these diverse and functionally fascinating molecules. Developmental genetics allied with biochemical, structural, and molecular studies will provide for a complete understanding of glycoconjugates that can readily be applied to other systems and animals, including humans. A major challenge at present is understanding how glycoconjugates alter the activity of their protein or lipid acceptors in signaling and developmental patterning. Likewise, the cellular activities governed by glycans are only beginning to be described. For example, how do proteoglycans affect the levels of morphogens in the matrix? Do proteoglycans affect the stability, endocytosis, or diffusion of these critical patterning molecules? These issues can all be addressed with the tools available in Drosophila and the fruitlfly promises to remain a valuable tool in understanding glycoconjugate function in vivo.