The existence of a local renin-angiotensin system in the heart is still a controversial issue. This review discusses the evidence, obtained from studies in cardiac cells, in isolated perfused hearts and in intact animals and humans, both under normal and pathological conditions, for local production of prorenin, renin, angiotensinogen, angiotensin-converting enzyme, angiotensin I and angiotensin II at cardiac tissue sites. In addition, the role of alternative angiotensin-generating enzymes (cathepsin, chymase) and the possibility of (pro)renin uptake from the circulation is evaluated.