The atrial natriuretic factor represents a group of atrial peptides structurally and functionally related. These peptides produce the following effects: natriuresis, diuresis, vasodilation and inhibition of aldosterone release. Its discovery in 1981 opened a new horizon in the studies on body sodium and water homeostasis, as well as on blood pressure regulation. In a few years there have been spectacular advances in the knowledge of this new hormone. However, there are still many doubts and controversies concerning its exact physiological role. Its effects on renal function, vascular contractility and its relationship with other physiological systems are not completely understood. The versatility of functions in which atrial natriuretic factor participates has pointed new trends in the research of important clinical entities such as arterial hypertension and cardiac failure, and could be a starting point for the development of novel therapeutic agents. In this work, the experimental findings dealing with the participation of atrial natriuretic factor in several biological events are reviewed.