The sinoatrial node (SAN) is the normal pacemaker of the mammalian heart. Over several decades, a large amount of data on the ionic mechanisms underlying the spontaneous electrical activity of SAN pacemaker cells has been obtained, mostly in experiments on single cells isolated from rabbit SAN. This allowed the development of comprehensive mathematical models of the electrical activity of rabbit SAN pacemaker cells. Recently, electrophysiological data have been obtained from human SAN pacemaker cells. We are working on a comprehensive model of the electrical activity of a human SAN pacemaker cell, using these electrophysiological data from human cells. Our human SAN cell model could be a useful tool in the design of experiments and the development of drugs that aim to modulate heart rate.