OBJECTIVE To investigate whether brief fasting before the induction of hypotension by non-lethal haemorrhage may induce translocation of enteric bacteria to mesenteric lymph nodes or blood in rats. METHODS Laboratory experiment. METHODS University departments of surgery and microbiology, Sweden. METHODS 39 Male Sprague-Dawley rats. METHODS 20 animals were fasted for 24 hours, all 39 then underwent controlled haemorrhage for 60 minutes that reduced the blood pressure to 55 mm Hg. METHODS Differences in blood loss, blood glucose concentrations, and packed cell volume; and aerobic cultures of mesenteric lymph nodes and blood. RESULTS Fasted rats (n = 20) lost 2.3% of blood volume compared with 2.8% in fed rats (p < 0.001). Packed cell volume dropped by 11.3% in fasted rats and 16.5% in fed rats (p < 0.001). Glucose concentrations rose by 7.0 mmol/l in fasted rats compared with 21.0 mmol/l in fed rats (p < 0.001). Mesenteric lymph nodes contained enteric bacteria in 14/20 fasted rats compared with 6/19 fed rats (p < 0.05). In 4 fasted rats blood cultures grew pathogenic bacteria compared with no fed rats (p = 0.11). The number of bacteria found in mesenteric lymph nodes was significantly greater in fasted than in fed rats (p = 0.01). CONCLUSIONS Brief fasting before hypotension caused by non-lethal haemorrhage was associated with significantly increased bacterial translocation compared with fed animals. Increases in blood glucose concentrations and plasma refill may have had a protective effect in fed rats. These experiments may be of clinical relevance as elective operations are usually preceded by overnight fasting.