BACKGROUND Diclofenac is commonly used for acute pain in children, but is not licensed for this indication in all age groups. OBJECTIVE 1) Assess the efficacy of diclofenac for acute pain in children. 2) Assess the safety of diclofenac for short-term use in children. 3) Identify gaps in the evidence to direct future research. METHODS Seventeen databases indexing clinical trial reports were searched in February 2005 (with an update search as part of this first review in May 2008). A hand search of Paediatric Anaesthesia was undertaken and summaries obtained of adverse reaction reports from the UK Yellow Card Scheme and World Health Organization (WHO) Monitoring Centre. The reference lists of included studies were also searched. METHODS Any published report, in any language, involving the administration of diclofenac to a patient aged 18 years or younger for acute pain and detailing either monitoring of efficacy or safety. METHODS Two review authors independently assessed study quality and extracted the data. Authors were contacted where necessary. Review Manager version 5 was used for analysis. RESULTS 1) EFFICACY: randomised controlled trials (RCTs) comparing diclofenac with placebo/any other treatment by using pain scores (assessed or reported), or need for rescue analgesia.2) SAFETY: any type of study seeking adverse events (regardless of cause). An adverse event was defined as any reported adverse or untoward happening to a patient being treated with diclofenac for acute pain.Seven publications on diclofenac efficacy and 79 on safety (74 studies plus five case reports) were included in the final analysis. Compared with placebo/no treatment, diclofenac significantly reduced need for post-operative rescue analgesia (relative risk [RR] 0.6; number needed to treat to benefit [NNT] 3.6; 95% confidence interval [CI] 2.5 to 6.3).Compared with any other non-NSAID, patients receiving diclofenac suffered less nausea or vomiting, or both (RR 0.6; NNT 7.7 [5.3 to 14.3]). There appeared to be no increase in bleeding requiring surgical intervention in patients receiving diclofenac in the peri-operative period. Serious diclofenac adverse reactions occurred in fewer than 0.24% of children treated for acute pain. The types of serious adverse reactions were similar to those reported in adults. CONCLUSIONS Diclofenac is an effective analgesic for perioperative acute pain in children. It causes similar types of serious adverse reactions in children as in adults, but these are rare. More research on optimum dosing and safety in asthmatic children is required.