Publisher Summary Diacylglycerol (DAG) is a prolific second messenger that activates proteins involved in a variety of signaling cascades. Because it can associate with a diverse set of proteins, DAG potentially activates numerous signaling cascades. Thus, its accumulation needs to be strictly regulated. Diacylglycerol kinases (DGKs), which phosphorylate DAG, are widely considered to be responsible for terminating diacylglycerol signaling. Diacylglycerol kinases are expressed in all multicellular organisms that have been studied. Their structural diversity and complexity indicate that they are functionally important in a variety of cellular signaling events. Since they can affect both DAG and phosphatidic acid (PA) signals, DGK activity plays a central role in many lipid signaling pathways. Activation of DGKs is complex, requiring translocation to a membrane compartment as well as binding to appropriate co-factors. Additional regulation of their activity occurs by posttranslational modifications.