Collagenopathic cardiopathies are a subject of extreme etiologic, pathogenetic and clinical interest. These disorders are associated with congenital or acquired anomalies of the connective tissue and because of the diffusion and nearly total distribution of this tissue, have a higher frequency than what has been previously estimated. The collagenopathic cardiopathies, can be divided into two main groups: one deriving from hereditary connective tissue diseases, and the other from acquired connective tissue diseases. The first group has a Mendelian type of transmission whereas the other appears to be secondary to various kinds of stimuli (viral, immunologic etc.) although polygenic factors are present. Of the first group we considered Marfan's syndrome, the Ehlers-Danlos syndrome, osteogenesis imperfecta, pseudoxanthoma elasticum, cutis laxa and the diseases of the fundamental substance with particular reference to mucopolysaccharidosis type 1H (Hurler's syndrome). In all of these disorders a specific metabolic disturbance is responsible for the cardiovascular damage which is expressed, depending on the specific genetic component in a more or less serious form. Among the acquired diseases of the connective tissue, we examined rheumatoid arthritis, systemic lupus erythematosus, polydermatomyositis, scleroderma; of the reactive arthritis, rheumatic fever; of the seronegative forms, spondyloarthritis, ankylosing spondylitis and Reiter's syndrome, mixed connective tissue disease and Lyme's disease. It must be emphasized that all of these disorders share relatively common pathogenetic characteristics which point to the importance of the presence of various types of antigens, immune complexes and the significant role of some of the histocompatibility antigens, as well as possible disturbances of cell-mediated immunity.(ABSTRACT TRUNCATED AT 250 WORDS)