BACKGROUND: The removal of the acute appendix is one of the most frequently performed surgical procedures. Open surgery associated with therapeutic efficacy has been the treatment of choice for acute appendicitis. However, in consequence of the evolution of endoscopic surgery, the operation can also be performed with minimally invasive surgery. Due to smaller incisions, the laparoscopic approach may be associated with reduced postoperative pain, reduced wound infection rate, and shorter time until return to normal activity.This is an update of the review published in 2010. OBJECTIVES: To compare the effects of laparoscopic appendectomy (LA) and open appendectomy (OA) with regard to benefits and harms. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL), Ovid MEDLINE and Embase (9 February 2018). We identified proposed and ongoing studies from World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP), ClinicalTrials.gov and EU Clinical Trials Register (9 February 2018). We handsearched reference lists of identified studies and the congress proceedings of endoscopic surgical societies. SELECTION CRITERIA: We included randomised controlled trials (RCTs) comparing LA versus OA in adults or children. DATA COLLECTION AND ANALYSIS: Two review authors independently selected studies, assessed the risk of bias, and extracted data. We performed the meta-analyses using Review Manager 5. We calculated the Peto odds ratio (OR) for very rare outcomes, and the mean difference (MD) for continuous outcomes (or standardised mean differences (SMD) if researchers used different scales such as quality of life) with 95% confidence intervals (CI). We used GRADE to rate the quality of the evidence. MAIN RESULTS: We identified 85 studies involving 9765 participants. Seventy-five trials included 8520 adults and 10 trials included 1245 children. Most studies had risk of bias issues, with attrition bias being the largest source across studies due to incomplete outcome data.In adults, pain intensity on day one was reduced by 0.75 cm on a 10 cm VAS after LA (MD -0.75, 95% CI -1.04 to -0.45; 20 RCTs; 2421 participants; low-quality evidence). Wound infections were less likely after LA (Peto OR 0.42, 95% CI 0.35 to 0.51; 63 RCTs; 7612 participants; moderate-quality evidence), but the incidence of intra-abdominal abscesses was increased following LA (Peto OR 1.65, 95% CI 1.12 to 2.43; 53 RCTs; 6677 participants; moderate-quality evidence).The length of hospital stay was shortened by one day after LA (MD -0.96, 95% CI -1.23 to -0.70; 46 RCTs; 5127 participant; low-quality evidence). The time until return to normal activity occurred five days earlier after LA than after OA (MD -4.97, 95% CI -6.77 to -3.16; 17 RCTs; 1653 participants; low-quality evidence). Two studies showed better quality of life scores following LA, but used different scales, and therefore no pooled estimates were presented. One used the SF-36 questionnaire two weeks after surgery and the other used the Gastro-intestinal Quality of Life Index six weeks and six months after surgery (both low-quality evidence).In children, we found no differences in pain intensity on day one (MD -0.80, 95% CI -1.65 to 0.05; 1 RCT; 61 participants; low-quality evidence), intra-abdominal abscesses after LA (Peto OR 0.54, 95% CI 0.24 to 1.22; 9 RCTs; 1185 participants; low-quality evidence) or time until return to normal activity (MD -0.50, 95% CI -1.30 to 0.30; 1 RCT; 383 participants; moderate-quality evidence). However, wound infections were less likely after LA (Peto OR 0.25, 95% CI 0.15 to 0.42; 10 RCTs; 1245 participants; moderate-quality evidence) and the length of hospital stay was shortened by 0.8 days after LA (MD -0.81, 95% CI -1.01 to -0.62; 6 RCTs; 316 participants; low-quality evidence). Quality of life was not reported in any of the included studies. AUTHORS' CONCLUSIONS: Except for a higher rate of intra-abdominal abscesses after LA in adults, LA showed advantages over OA in pain intensity on day one, wound infections, length of hospital stay and time until return to normal activity in adults. In contrast, LA showed advantages over OA in wound infections and length of hospital stay in children. Two studies reported better quality of life scores in adults. No study reported this outcome in children. However, the quality of evidence ranged from very low to moderate and some of the clinical effects of LA were small and of limited clinical relevance. Future studies with low risk of bias should investigate, in particular, the quality of life in children.