In today's field of plant cell wall research, insights into the structure of wall components are obtained using many different techniques, ranging from spectroscopic and microscopic to chemical and biochemical. In this chapter, we describe one method: oligosaccharide mass profiling (OLIMP). Using OLIMP, we can harness the selective power of a specific wall hydrolase together with the speed and sensitivity of mass spectrometry to provide highly reproducible structural and compositional information about the wall molecule of interest.