Double-checking of medication administration by two qualified health professionals is meant to reduce the risk of medication errors. However, prior experience with this practice has raised numerous potential problems. This systematic review examined the limited evidence base for medication administration double-checking. The majority of included studies were qualitative and consisted of asking nurses whether they felt double-checking was likely to result in fewer medication errors. Three quantitative studies showed a modest decrease in error rates. The authors found insufficient evidence to either support or refute the practice of double-checking. Despite this lack of evidence, manual double-checking has been a previously recommended strategy and has become standard policy for high-risk medications at many hospitals.