Extraordinary progress has been made in refining our understanding of the B-cell antigen receptor complex, the role of protein-tyrosine phosphorylation as the key intermediary in immunoglobulin signal transduction, and in identifying candidate effectors of immunoglobulin-mediated signaling. In addition, the properties of a new group of G proteins may rekindle interest in older observations implicating such molecules as important in B-cell activation.