To understand the determinants of chondrocyte FGF inhibitory response we sought to identify the unique set of proteins whose phosphorylation status is changed upon FGF treatment. RCS (Rat ChondroSarcoma) (RCS) cells were used for our experiments as a well-accepted model of proliferative chondrocytes which respond to FGF signaling with growth arrest Chondrocytes were treated with FGF1 and, as a control, cell cycle changes were monitored by FACScan analysis to demonstrate strong (around 95%) downregulation of S-phase at 24h. Three independent experiments were performed to obtain statistically representative datasets. We quantified 8299 proteins were quantified in the global proteome analysis using only unique or and razor peptides for quantitation . All proteins were identified in at least two replicates of a single treatment set by 2 or more peptides with 1% FDR Inclusion requirements for a single proteins were 1) two or more peptides identified with 51% FDR and 2) peptides that proteins were identified in at least 2 replicates of a single sample set.