SI',Jere histamine mediated reactions to intrw(}clloltS drltgs ltsed ill anaesthesia may occur as a result of anaphylactic and anaphylactoid reactions. The incidence is rare, but appears to be increasing, The difficulties in diagnosing sltch reactions and in determining the dm{!. responsible and ho1.£' these difficulties hm.'c led to confllsionin the literatllre are discussed. Six cases of SC1 ' cre histamine mediated reactions are presented and detailed analyses of the drugs in these and other reported reactions is made sho1.£'ing l ' aried clinical patterns It'itll different dmgs. The prel'clltioJ1, treatment, and fol101c-up of SC1 ' ere histamine mediated reactions are considered.