BACKGROUND Surgeons who perform laparotomy have a number of decisions to make regarding abdominal closure. Material and size of potential suture types varies widely. In addition, surgeons can choose to close the incision in anatomic layers or mass ('en masse'), as well as using either a continuous or interrupted suturing technique, of which there are different styles of each. There is ongoing debate as to which suturing techniques and suture materials are best for achieving definitive wound closure while minimising the risk of short- and long-term complications. OBJECTIVE The objectives of this review were to identify the best available suture techniques and suture materials for closure of the fascia following laparotomy incisions, by assessing the following comparisons: absorbable versus non-absorbable sutures; mass versus layered closure; continuous versus interrupted closure techniques; monofilament versus multifilament sutures; and slow absorbable versus fast absorbable sutures. Our objective was not to determine the single best combination of suture material and techniques, but to compare the individual components of abdominal closure. METHODS On 8 February 2017 we searched CENTRAL, MEDLINE, Embase, two trials registries, and Science Citation Index. There were no limitations based on language or date of publication. We searched the reference lists of all included studies to identify trials that our searches may have missed. METHODS We included randomised controlled trials (RCTs) that compared suture materials or closure techniques, or both, for fascial closure of laparotomy incisions. We excluded trials that compared only types of skin closures, peritoneal closures or use of retention sutures. METHODS We abstracted data and assessed the risk of bias for each trial. We calculated a summary risk ratio (RR) for the outcomes assessed in the review, all of which were dichotomous. We used random-effects modelling, based on the heterogeneity seen throughout the studies and analyses. We completed subgroup analysis planned a priori for each outcome, excluding studies where interventions being compared differed by more than one component, making it impossible to determine which variable impacted on the outcome, or the possibility of a synergistic effect. We completed sensitivity analysis, excluding trials with at least one trait with high risk of bias. We assessed the quality of evidence using the GRADEpro guidelines. RESULTS Fifty-five RCTs with a total of 19,174 participants met the inclusion criteria and were included in the meta-analysis. Included studies were heterogeneous in the type of sutures used, methods of closure and patient population. Many of the included studies reported multiple comparisons.For our primary outcome, the proportion of participants who developed incisional hernia at one year or more of follow-up, we did not find evidence that suture absorption (absorbable versus non-absorbable sutures, RR 1.07, 95% CI 0.86 to 1.32, moderate-quality evidence; or slow versus fast absorbable sutures, RR 0.81, 95% CI 0.63 to 1.06, moderate-quality evidence), closure method (mass versus layered, RR 1.92, 95% CI 0.58 to 6.35, very low-quality evidence) or closure technique (continuous versus interrupted, RR 1.01, 95% CI 0.76 to 1.35, moderate-quality evidence) resulted in a difference in the risk of incisional hernia. We did, however, find evidence to suggest that monofilament sutures reduced the risk of incisional hernia when compared with multifilament sutures (RR 0.76, 95% CI 0.59 to 0.98, I2 = 30%, moderate-quality evidence).For our secondary outcomes, we found that none of the interventions reduced the risk of wound infection, whether based on suture absorption (absorbable versus non-absorbable sutures, RR 0.99, 95% CI 0.84 to 1.17, moderate-quality evidence; or slow versus fast absorbable sutures, RR 1.16, 95% CI 0.85 to 1.57, moderate-quality evidence), closure method (mass versus layered, RR 0.93, 95% CI 0.67 to 1.30, low-quality evidence) or closure technique (continuous versus interrupted, RR 1.13, 95% CI 0.96 to 1.34, moderate-quality evidence).Similarily, none of the interventions reduced the risk of wound dehiscence whether based on suture absorption (absorbable versus non-absorbable sutures, RR 0.78, 95% CI 0.55 to 1.10, moderate-quality evidence; or slow versus fast absorbable sutures, RR 1.55, 95% CI 0.92 to 2.61, moderate-quality evidence), closure method (mass versus layered, RR 0.69, 95% CI 0.31 to 1.52, moderate-quality evidence) or closure technique (continuous versus interrupted, RR 1.21, 95% CI 0.90 to 1.64, moderate-quality evidence).Absorbable sutures, compared with non-absorbable sutures (RR 0.49, 95% CI 0.26 to 0.94, low-quality evidence) reduced the risk of sinus or fistula tract formation. None of the other comparisons showed a difference (slow versus fast absorbable sutures, RR 0.88, 95% CI 0.05 to 16.05, very low-quality evidence; mass versus layered, RR 0.49, 95% CI 0.15 to 1.62, low-quality evidence; continuous versus interrupted, RR 1.51, 95% CI 0.64 to 3.61, very low-quality evidence). CONCLUSIONS Based on this moderate-quality body of evidence, monofilament sutures may reduce the risk of incisional hernia. Absorbable sutures may also reduce the risk of sinus or fistula tract formation, but this finding is based on low-quality evidence.We had serious concerns about the design or reporting of several of the 55 included trials. The comparator arms in many trials differed by more than one component, making it impossible to attribute differences between groups to any one component. In addition, the patient population included in many of the studies was very heterogeneous. Trials included both emergency and elective cases, different types of disease pathology (e.g. colon surgery, hepatobiliary surgery, etc.) or different types of incisions (e.g. midline, paramedian, subcostal).Consequently, larger, high-quality trials to further address this clinical challenge are warranted. Future studies should ensure that proper randomisation and allocation techniques are performed, wound assessors are blinded, and that the duration of follow-up is adequate. It is important that only one type of intervention is compared between groups. In addition, a homogeneous patient population would allow for a more accurate assessment of the interventions.