Background: Flecainide is an antiarrhythmic agent that is used primarily in the treatment of cardiac arrhythmias. Some evidences also suggest that flecainide can participate in alveolar fluid clearance and inflammatory responses. This experiment was aimed to evaluate the effects of flecainide on sepsis induced acute lung injury in a rat model. Methods: Rats were treated with subcutaneous infusion of saline or flecainide (0.1 or 0.2 mg/kg/hr) by a mini-osmotic pump. Subcutaneous infusion was started 3 hours before and continued until 8 hours after intraperitoneal injection of saline or endotoxin. Animals were sacrificed for analyses of severity of acute lung injury with wet to dry (W/D) ratio and lung injury score (LIS) in lung and inflammatory responses with level of leukocyte, polymorphonuclear neutrophils (PMNs) and inteleukin-8 (IL-8) in bronchoalveolar lavages fluid (BALF). Results: Flecainide markedly improved dose dependently sepsis induced acute lung injury as analysed by W/D ratio (from 2.24 ± 0.11 to 1.76 ± 0.09, p < 0.05) and LIS (from 3 to 1, p < 0.05), and inflammatory response as determined by leukocyte (from 443 ± 127 to 229 ± 95, p < 0.05), PMNs (from 41.43 ± 17.63 to 2.43 ± 2.61, p < 0.05) and IL-8 (from 95.00 ± 15.28 to 40.00 ± 10.21, p < 0.05) i...