Glucans are insoluble polymers of beta-1,3-linked glucose derived from yeast cell walls that effectively activate macrophages. Recently, aminated derivatives of beta-1,3-D-polyglucose have been developed that are soluble but also activate murine macrophages. The current studies were undertaken to determine whether soluble aminated beta-1,3-D-polyglucose (AG) would also stimulate human monocytes. The AG employed contained less than 2 ng endotoxin/mg. AG induced the production of intracellular, membrane-associated, and secreted forms of interleukin 1 (IL1) in a dose-dependent manner, with 50 micrograms/ml yielding maximal responses. AG also induced tumor necrosis factor-alpha (TNF alpha) secretion by human monocytes. Prostaglandin E2 (PGE2) production was also stimulated in a concentration-dependent manner. Quantitatively, optimal stimulatory concentrations of AG were comparable to endotoxin in the capacity to induce production of these various mediators. In contrast to its capacity to induce production of IL1, TNF alpha, and PGE2, AG did not stimulate monocytes to become more effective antigen presenting cells. These results indicate that AG is potent inducer of proinflammatory mediators from human monocytes but does not enhance their capacity to initiate immune responses.