Receptors of the Notch family mediate cell-cell interactions during animal development, and aberrations in Notch signaling have been implicated in human disease. Studies in Caenorhabdits elegans have made essential contributions towards understanding the biological roles and molecular mechanism of this fundamental signaling system. A major development in the field since the original version of this chapter (LIN-12/Notch signaling in C. elegans) has been an explosion in information about the structural biology of Notch signaling; crystallographic determinations of structures, including structures of C. elegans components, have contributed much to the current understanding of molecular mechanism. Thus, here, we not only cover the genetics of Notch in C. elegans, focusing on conserved core components and modulators, we have also included structural information about these components, describing the key events occurring during ligand binding and transcriptional control of target genes. In addition to text, we include Tables listing core components and key modulators of the signaling pathway along with their orthologs in Drosophila and mammals, a Table listing validated target genes in various processes in C. elegans, and animated features to illustrate structural attributes.