Calcium is a universal intracellular signal that is responsible for controlling a plethora of cellular processes. Understanding how such a simple ion can regulate so many diverse cellular processes is a key goal of calcium- and cell-biologists. One molecule that is sensitive to changes in intracellular calcium levels is Ras. This small GTPase operates as a binary molecular switch, and regulates cell proliferation and differentiation. Here, we focus on examining the link between calcium and Ras signalling and, in particular, we speculate as to how the complexity of calcium signalling could regulate Ras activity.