Patients may control postoperative pain by self-administration of intravenous opioids using devices designed for this purpose (patient controlled analgesia or PCA). Two previous meta-analyses found patients preferred PCA versus conventional analgesia but disclosed no differences in analgesic consumption or length of postoperative hospital stay. Results were equivocal regarding differences in pain intensity or relief between groups. We performed an updated and expanded analysis to fully explore differences between PCA and conventional analgesia.Randomized controlled trials (RCTs) were identified from MEDLINE, the Cochrane Central Register of Controlled Trials and EMBASE. RCTs that compared PCA without a continuous background infusion versus conventional parenteral analgesia and that employed pain intensity as an outcome were selected. Meta-analyses were performed of outcomes that included analgesic efficacy, analgesic consumption, patient satisfaction, length of stay and side effects.PCA provides better pain control and greater patient satisfaction than conventional parenteral analgesia. Patients using PCA consume higher amounts of opioids than controls, and have a higher incidence of pruritus, but a similar incidence of other side effects. There is no difference in the length of stay.This review provides evidence that PCA is an efficacious alternative to conventional systemic analgesia for postoperative pain control.