Background As an alternative to electric vacuum aspirations (EVA), there is an increasing interest in using manual vacuum aspiration (MVA).Objective To compare the safety, efficacy and acceptability of MVA with those of EVA for first-trimester abortion.Search strategy We searched MEDLINE, EMBASE, Cochrane Library and Chinese Biomedical Database in all language, together with reference lists of retrieved papers.Selection criteria Randomised controlled trials comparing MVA with EVA for first-trimester abortion were included. The outcomes are complete abortion rate, uterine perforation rate, blood loss, pain perception and acceptability.Data collection and analysis Two reviewers independently extracted the data. Results from the trials were combined to calculate relative risks (RRs) or risk differences for dichotomous outcomes and weighted mean differences (WMDs) for continuous outcomes, together with 95% CIs.Main results Ten trials were included, involving 1660 women. Generally, the methodological quality was poor. There were no statistically significant differences, comparing MVA with EVA, in complete abortion rate (RR 1.00; 95% CI 0.99-1.02) and participants' satisfaction (RR 1.02; 95% CI 0.87-1.20). In participants with less than 50 days of gestational age, less blood loss (WMD -1.84; 95% CI -2.45 to -1.23) and less severe pain perception (RR 0.04; 95% CI 0.01-0.12) were reported during the MVA procedure, whereas the operation time was shorter (WMD 0.32; 95% CI 0.02-0.63) in the EVA procedure.Author's conclusions There is some evidence that MVA is as effective and acceptable as EVA and might be safer than EVA.Keywords Abortion, electric vacuum aspirations, manual vacuum aspiration, meta-analysis, randomised controlled trial, systematic review.Please cite this paper as: Wen J, Cai Q, Deng F, Li Y. Manual versus electric vacuum aspiration for first-trimester abortion: a systematic review. BJOG 2008;115:5-13.