With emphasis on the pulmonary circulation, three general types of vascular disease are discussed: fibroproliferative (atherosclerosis), cellular proliferative (endothelial neoplasms) and inflammatory (granulomatous vasculitis). The causes of these phenotypic responses are invariably multifactorial, but infectious agents including viruses, Chlamydia, Helicobacter, Rickettsia, mycobacteria and other infectious agents have been increasingly implicated in the pathophysiology. The classifications of vascular diseases are complicated and confusing and many eponymous diseases are specific variations of more general disease processes. The pivotal role of the monocyte/macrophage and T-cells is discussed, particularly with regard to intracellular infections. In addition to antimicrobial therapy, modifications of macrophage function by IFN-gamma and blockade of TNF are attractive areas for therapeutic research. Diseases with many synergistic causes will probably also require multifaceted therapeutic interventions.