The advent of new forms of therapy in the treatment of Hodgkin's disease requires accurate clinical staging. Although many patients with Hodgkin's disease have evidence of marrow involvement at autopsy, examination of the marrow during life by aspiration techniques infrequently demonstrates this. This difference relates both to the fibrous and granulomatous nature of the lesion which prevents aspiration of marrow particles and to the disruption of marrow architecture by aspiration. In contrast, closed needle biopsy of the posterior iliac crest overcomes these limitations. Of 49 patients studied, 11 had positive biopsy evidence of Hodgkin's disease even though aspiration studies had been unrevealing. Of these 11, 6 had been classified initially as Stage III and thus required reclassification to Stage IV. Biopsy failed to demonstrate marrow involvement in 5 of 39 patients who had marrow involvement proved at autopsy. These data indicate that with positive findings, marrow biopsy can be a helpful tool for the more accurate staging of advanced Hodgkin's disease.