The adapter protein Grb10 belongs to a superfamily of related proteins that include Grb7, Grb14 and the Caenorhabtidis elegans Mig10. The available data on Grb10 proteins suggest a role of these adapters in signaling downstream of several receptor tyrosine kinases. In the present review the focus is on the interaction between Grb10 proteins and the insulin-like growth factor receptor/insulin receptor, and the role of Grb10 in IGF-I/insulin-induced mitogenesis is discussed, considering that the data available are also partially discordant.