In order to define the optimum timing of surgery for a hip fracture, we performed a systematic review of published evidence. Data was extracted by two independent reviewers and the methodology of each study was assessed. Fifty-two studies involving 291,413 patients were identified. Outcomes measured were mortality, post-operative complications, length of hospital stay and percentage of patients discharged home. We found no randomised trials. For the 25 studies involving 282,470 participants that undertook adjustment for confounding factors, early surgery was associated with a reduced hospital stay. These studies produced conflicting results regarding mortality and morbidity being increased or unaffected by delaying surgery. None of these studies reported any adverse outcomes for early surgery. Those studies with more careful methodology were less likely to report a beneficial effect of early surgery, particularly in relation to mortality. In conclusion early surgery (within 48h of admission) after a hip fracture reduces hospital stay and may also reduce complications and mortality.