An in vitro model for the study of sepsis mediators was used to investigate the effects of two different lipopolysaccharides (LPS), a smooth (LPS-S) and a rough (LPS-R) type, on the release of chemokines (IL-8 and MIP-1 alpha) and cytokines (TNF alpha, IL-1 beta, IL-1ra and IL-10) from human whole blood samples. TNF alpha level increased significantly vs. control, at 4 h and 8 h after the challenge with smooth and rough type of LPS respectively. Concentrations of the two chemokines studied, IL-8 and MIP-1 alpha, were significantly elevated following stimulation by both LPS, and reached concentrations significantly different from controls at 4, 8 and 24 h. After 24 h of incubation both LPS produced a significant IL-10 increase, although such change was more substantial with the rough type. Present data suggest an early and maintained release of chemokines regardless of the type of LPS used and often in absence of a significant increase in primary pro-inflammatory cytokines.