Liver regeneration is a prerequisite for extended liver surgery. Several studies have shown that the bacterial gut flora is able to modulate liver function. Previously we observed that synbiotics could partly reverse the impaired mitosis rate of hepatocytes in a rat model of synchronous liver resection and colon anastomosis. The effect of synbiotics on liver function after hepatic resection has not been analysed yet. A prospective randomised double-blind pilot trial was undertaken in 19 patients scheduled for right hepatectomy. All patients received enteral nutrition immediately post-operatively. Comparison was made between a group receiving a combination of four probiotics and four fibres and a placebo group receiving the fibres only starting the day before surgery and continuing for 10 days. Primary study endpoint was the liver function capacity measured by 13C-methacetin breath test and indocyanine green plasma disappearance rate. Portal vein flow, liver volumetry, laboratory parameters for liver function, length of hospital stay, post-operative complications and side effects of synbiotic therapy were recorded. Liver function capacity was comparable in both groups. Complications had a negative impact on liver function. Because complications were more severe in the verum group, a sub-analysis was performed. In case of an uncomplicated course, liver function capacity was better in the patients with synbiotics. No severe side effects occurred. Synbiotics might be able to increase liver function capacity in patients after liver resection, but patient numbers were too small and the clinical courses too heterogeneous to draw any definite conclusions.