Maize, sorghum, sugarcane, switchgrass and miscanthus are the main crops suggested as potential sources of lignocellulosic biomass for the production of second-generation ethanol. The attention these crops have received has been concentrated in the field of genomics, and very little research has been performed in the field of proteomics, particularly in the cell wall proteomic, despite the importance of these crops in biofuel production. New mass spectrometry-based proteomic methods allow the identification and quantification of thousands of proteins in complex mixtures, as well as the detection of post-translational changes in complex proteomes, providing important insight into the downstream consequences of gene expression. Together with other ‘omic’ approaches, proteomic might be decisive to bring new information in the study of cell wall formation. Here, we briefly highlight proteomic techniques and review the research that has been completed on the proteomes of these five crops.