Surgery remains the most effective treatment for most cancers, but it is usually associated with systemic release of tumour cells; additionally, preexisting scattered micrometastases commonly remain. Whether minimal residual disease succeeds in establishing itself as recurrence or metastases is primarily a function of host defence. In practice, the immune system frequently fails to neutralize remaining malignant tissues. Considerable in-vitro data and in-vivo animal studies suggest that three factors associated with cancer surgery impair cellular immunity: the stress response to tissue injury, general anaesthesia, and opioid analgesia. Regional analgesia decreases the neuroendocrine stress response to surgical tissue injury, eliminates or reduces the need for general anaesthesia, and minimizes opioid requirement. I therefore propose the hypothesis that cancer recurrence is lower after surgery with regional anaesthesia/analgesia than after surgery with general anaesthesia and opioid analgesia. Confirming this hypothesis would indicate that a minor modification to anaesthetic management reduces the risk of cancer recurrence.