To gain insights into the signalling pathways regulated by Leukocyte common antigen-related protein (LAR), including those that are PDGF-dependent, we have carried out the first systematic analysis of LAR-regulated signal transduction using SILAC-based quantitative proteomic and phosphoproteomic techniques. We have analysed differential phosphorylation between wild-type mouse embryo fibroblasts (MEFs) or MEFS in which the LAR cytoplasmic phosphatase domains had been deleted (LARΔP).