The histological features of eighty cardiac myxomas removed by surgery between 1959 and 1988 were evaluated by the usual staining techniques and also by identification of immunohistological markers (vimentin, desmin, factor VIII, actin). Myxoma cells present various forms (polygonal, round, spindle, stellate) when isolated but are characterized by their tubular angioid structures: cellular masses, elementary tubes, organoid formations with several parietal layers and abundant "myxoid" matrix, denser around the angioid structures. Sometimes they are located on the surface forming crypts and vegetations, replaced in old myxomas by hyalinization. Other constituents such as vascular spaces, fibrinous exudate, hemosiderosis pigments, necrobiotic areas, various calcifications, plasma cell infiltrates are also frequently found. The insertion on the endocardium is usually an interesting structure. The presence of mucous epithelial structures and clusters of smooth muscle cells is uncommon but constitutes an additional argument in favour of the present explanation concerning its histogenosis i.e. a tumor derived from vestigial cells, usually confined to the floor of the fossa ovalis. On the basis of these various characteristics, myxomas can be classified as being active or inactive (more or less mummified), poorly differentiated or mature, which may correspond to the duration of the lesion prior to its resection. A precise histological examination of myxoma avoids confusion with more malignant myxomatous cardiac tumors.