The presence or absence of composite nodules, corresponding to recently described structural and functional units in the human reactive lymph node, was investigated in 22 lymph nodes involved by Hodgkin's disease using in situ immuno- and enzymehistochemical techniques. In 10/13 cases of nodular sclerosing subtype, typical composite nodules composed of adjacent B- and T-domains and surrounded by a rim of high endothelial venules were recognized. In association with these venules, a concentrical rim of fusiform shaped Alk Phase+ fibroblastic reticulum cells was observed. Reed-Sternberg cells and their morphological variants were exclusively found in the T-area of these composite nodules. In 5/6 cases of mixed cellularity Hodgkin's disease, B lymphoid follicles were apparent. No vascular relationship with the tumourally involved areas was noticed. In the remaining cases, including all cases of lymphocytic depletion Hodgkin's disease only scattered B cell clusters were recognized. Our observations indicate the persistence of an organoid structure, i.e. the composite nodule in nodular sclerosing Hodgkin's Disease (HD).