The most important example of intravascular infection is infective endocarditis (IE), a common and serious disorder in man. In the past, these infections were uniformly fatal, but since the development of potent antimicrobial agents, bac­ teriological cure has become practical and predictable. So, for a while, it seemed that intravascular infection would diminish in importance and be relegated to the skpile of illnesses which physicians, one or two generations earlier, used to see frequently. In recent years, however, spectacular technological advances (cardiac surgery, intravascular devices, hemodialysis), accompanied by profound social deterioration (intravenous drug usage), have provided new breeding grounds for the development of these infections. So it is that a large percentage of intravascular infections may be looked upon today as one of the diseases of medical progress and social evolution. This "progress," however, has not only contributed to the encouragement of the disease; there is another side to the coin: the same technological advances that have served to increase the frequency of infection (e. g. , intravascular plastic catheters) have also led to the first simple, easily reproducible laboratory animal model for the study of the disease, thus advancing our understanding of the prophylaxis, treatment, and general biology of these infections (Figures 1 and 2). Similarly, whereas the insertion of prosthetic heart valves has created a new group of patients with endocarditis, these same surgical techniques are lifesaving to patients with endocarditis whose aortic valves have perforated.