Healing of surgical and traumatic wounds mainly involves the clotting process, inflammation, cell proliferation and tissue remodelling. Healing time depends on the depth of the wound. In order to identify drugs that can slow the healing process, we reviewed comparative clinical trials, epidemiological studies and detailed case reports, using the standard Prescrire methodology. Delayed healing of surgical or traumatic wounds is associated with persistent bleeding, increased wound seepage and, in some cases, failed wound closure. Delayed wound healing can have severe and sometimes life-threatening consequences, including deep-seated infection, prolonged hospitalisation, repeat surgery to join or rejoin the wound edges, and delayed functional recovery of a transplanted organ. Delayed healing may be due to failure of one or several steps in the healing process, caused by metabolic, cardiovascular, infectious, immunological or drug-related disorders. The principal drugs that can slow wound healing are cytotoxic antineoplastic and immunosuppressive agents, corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), and anticoagulants. In practice, when wound healing is delayed, it is best to keep in mind that a drug may be the cause, and to consider withdrawing any drug or drugs known to have this effect, in order to allow the wounds to heal.