Unstable angina is a clinical syndrome which results from the unstabilization of the coronary atherosclerothic plaque, leading to its ulceration or rupture and to the formation of superimposed thrombus. The mechanism underlying plaque unstabilization is a subject of intense basic research. In the last few years, new knowledge has emerged that relates inflammation in the atherosclerothic lesion with its gradual growth and development, as well as with its sudden transformation into a complicated plaque causing unstable angina or myocardial infarction. In this article we will review the evidence that links inflammation with the pathogenesis of unstable angina and its prognosis.