Protein tyrosine phosphatases (PTPases) SHP1 and SHP2 are critical regulators in the intracellular signaling pathways that result in cell responses such as mitosis, differentiation, migration, survival, transformation or death. SHP2 is a signal transducer for several receptor tyrosine kinases and cytokine receptors. A novel SHP2 associated glycoprotein was recently cloned from human, rat, mouse and cattle by several labs and was designated SIRPa (1),SHPS1 , MyD1, BIT and p84. SIRPa is a new gene family containing at least fifteen members. SIRPa is a substrate of many activated tyrosine kinases such as insulin receptor, EGFR, PDGFR and src, and a specific docking protein for SHP2. SIRPa has regulatory effects on cellular responses induced by serum, growth factors, insulin, oncogenes, growth hormones and cell adhesion and plays a general role in different physiological and pathological processes.