ObjectiveTo systematically review the efficacy of transdermal fentanyl versus oral morphine for moderate/severe cancer pain. MethodsDatabases such as The Cochrane Library (Issue 1, 2014), PubMed, Web of Science, CNKI, VIP, CBM and WanFang Data were searched for randomized controlled trials (RCTs) on the efficacy of transdermal fentanyl versus oral morphine for moderate/severe cancer pain up to January 2014. According to inclusion and exclusion criteria, two reviewers independently screened literature, extracted data, and assessed methodological quality of included studies. Then meta-analysis was performed using RevMan 5.1.0 software. ResultsA total of 35 RCTs involved 3 406 patients were included. The results of meta-analysis showed that, there was no significant difference in effectiveness between transdermal fentanyl and oral morphine for moderate/severe cancer pain (OR=1.00, 95%CI 0.80 to 1.27, P=0.99). Compared with oral morphine, transdermal fentanyl was better in lowering the incidences of constipation, nausea and vomiting, lethargy and urinary retention; but transdermal fentanyl increased the incidences of skin rashes and itch (P < 0.05). ConclusionTransdermal fentanyl is as effective as oral morphine in the treatment of moderate/severe cancer pain, and transdermal fentanyl causes less side effects. Due to poor quality of the included studies, the above conclusion should be verified by further conducting more high quality RCTs.