Lipoglycans represent a special type of lipopoly-saccharide that differs in structure from the well-known gram-negative bacteria lipopolysaccharide. After briefly describing their most important characteristics, the authors take into consideration the in vitro interaction between lipoglycans from Acholeplasma granularum, Acholeplasma oculi, and Acholeplasma axanthum and human leukocytes in terms of production of procoagulant activity. The results obtained show that the examined lipoglycans possess, similarly to lipopolysaccharides, the capacity to induce the production of procoagulant activity, thromboplastin-like, from human mononuclear cells. However, the pathophysiological significance of this endotoxin-like activity remains to be established.