Objective: To investigate the potential beneficial and adverse effects of early post-pyloric feeding compared with gastric feeding in critically ill adult patients with no evidence of impaired gastric emptying. Design: Randomised controlled studies comparing gastric and post-pyloric feeding in critically ill adult patients from Cochrane Controlled Trial Register (2005 issue 3), EMBASE and MEDLINE databases (1966 to 1 October 2005) without any language restriction were included. Two reviewers reviewed the quality of the studies and performed data extraction independently. Measurements and results: Eleven randomised controlled studies with a total of 637 critically ill adult patients were considered. The mortality (relative risk [RR] 1.01, 95% CI 0.76-1.36, p = 0.93; I-2 = 0%) and risk of aspiration or pneumonia (RR 1.28, 95% CI 0.91-1.80, p = 0.15; I-2 = 0%) were not significantly different between patients treated with gastric or post-pyloric feeding. The effect of post-pyloric feeding on the risk of pneumonia or aspiration was similar when studies were stratified into those with and those without the use of concurrent gastric decompression (RR ratio 0.95, 95% CI 0.48-1.91, p = 0.89). The risk of diarrhoea and the length of intensive care unit stay (weighted mean difference in days -1.46, 95% CI -3.74 to 0.82, p = 0.21; I-2 = 24.6%) were not statistically different. The gastric feeding group had a much lower risk of experiencing feeding tube placement difficulties or blockage (0 vs 9.6%, RR 0.13, 95% CI 0.04-0.44, p = 0.001; I-2 = 0%). Conclusions: Early use of post-pyloric feeding instead of gastric feeding in critically ill adult patients with no evidence of impaired gastric emptying was not associated with significant clinical benefits.