A group of monoclonal antibodies was shown to react with glycoconjugates containing a sugar sequence--lacto-N-fucopentaose III (LNF-III)--in granulocytes and in some normal nonlymphoid cells. The antibodies including anti-Leu M1, anti-My-1, WGHS 29-1, 534F-8, and 538F-12 of the immunoglobulin M-type were used to study the biochemical properties of LNF-III antigens in granulocytes, interdigitating reticulum cells, and neoplastic cells of Hodgkin's disease. In contrast to the presence of an abundant LNF-III glycolipid in granulocytes, the Hodgkin's neoplastic cells had no LNF-III glycolipid or contained only minimal amounts; however, both LNF-III glycoconjugates isolated from Hodgkin's neoplastic cells and interdigitating reticulum cells appeared to be a similar, if not an identical, 150,000-molecular-weight glycoprotein. The neoplastic cells in Hodgkin's disease appeared to show a biochemical property more closely related to interdigitating reticulum cells than any other cells in the monocyte-granulocyte-histiocyte system.