An effective anaesthetic for oysters was sought, in order to allow for experimental manipulation of live oysters with minimal stress. A range of anaesthetics commonly used with gastropods and cephalopods, as well as a fish anaesthetic, were tested. Most of the chemicals tested were found to be unsuitable for oysters. Magnesium chloride was the most successful agent, inducing anaesthesia quickly, allowing rapid recovery with minimal stress and mortality. © 1992.