The histologic features in 171 cases of nodular lymphocyte-predominant (L&H) Hodgkin's disease are presented and the association with an abnormal form of follicular hyperplasia termed "progressively transformed germinal centers" (PTGC) by Lennert is discussed. PTGC may closely resemble the nodules of L&H Hodgkin's disease and in 18% of our cases the two processes coexisted in the same lymph node. In addition, two patients had lymph node biopsies showing PTGC prior to biopsies showing nodular L&H Hodgkin's disease and three patients with histologically proved Hodgkin's disease were found to have PTGC in subsequent lymph node biopsies. Immunologic studies on frozen tissue sections from three cases of nodular L&H Hodgkin's disease showed that the neoplastic nodules contained abundant dendritic reticulum cells and B-lymphocytes with scattered T-lymphocytes. These findings suggest that the association between PTGC and nodular L&H Hodgkin's disease is more than coincidental and that this form of Hodgkin's disease preferentially involves B-cell areas of the lymph node, in contrast to the T-zone distribution in other forms of this disorder.