Statins reduce plasma cholesterol, but clinical trials and in vitro studies indicate that they might also possess anti-inflammatory properties. The effect of simvastatin on circulating cytokines and leucocytes was evaluated in a human in vivo model of low-grade inflammation. Thirty young healthy male participants received an injection of the bacterial cell wall product endotoxin (0.06 ng/kg) to induce systemic inflammation. Participants were then randomized into a control and a simvastatin group. The simvastatin group received simvastatin 20 mg daily for 14 days. All participants returned after 14 days to receive a second endotoxin injection. Plasma concentrations of tumour necrosis factor (TNF)-alpha, interleukin (IL)-6 and IL-1 receptor antagonist were measured by enzyme-linked immunosorbent assay (ELISA) before and hourly for 6 hours after endotoxin administration. Plasma cytokines as well as total leucocyte counts increased in all participants upon endotoxin challenge but were not affected by simvastatin treatment. Tolerance to endotoxin was observed in both groups after 14 days. Short-term treatment with simvastatin (20 mg/day) did not influence circulating cytokine levels during endotoxaemia in this human in vivo study.