In the present study we have investigated the potential involvement of protein kinase C (PKC) in the maturation of human dendritic cells (DC) by bacterial lipopolysaccharide (LPS). LPS stimulation of DC derived from human monocytes resulted in PKC phosphorylation. Inhibition of PKC activation using bisindolylmaleimide (Bis), a pan‐PKC inhibitor, was associated with a dose‐dependent decrease of LPS‐induced IL‐12 production. In contrast, up‐regulation of MHC class II, CD80 and CD86 was not altered. Consistent with the diminished IL‐12 synthesis, DC stimulated with LPS in presence of Bis were deficient in the induction of IFN‐γ production by allogeneic CD4⁺ T cells. Furthermore, we found that PKC inhibition impaired LPS‐induced IκB‐α degradation and subsequent nuclear factor (NF)‐κB activation in DC. LPS resulted in the phosphorylation of conventional α/β and novel ϵ PKC isoforms in DC. Inhibition of LPS‐induced PKC activity using pseudosubstrate peptides specific for PKC isoforms established that PKC ϵ but not PKC α/β was involved in the production of IL‐12 and TNF‐α. Overall, these data provide evidence thatPKC inhibition impairs LPS signaling in DC and identify PKC ϵ as a potential target for the inhibition of Toll‐like receptor‐4‐mediated, IL‐12‐dependent Th1 type responses.