Three cases of convulsions are described, occurring in apparently normal children following premedication with Pamergan SP100, which is a proprietary mixture containing promethazine 50 mg, pethidine 100 mg, and hyoscine 0.4 mg in each ampoule. The aetiology is discussed. It is tentatively concluded that the convulsions are due to an idiosyncratic reaction to the promethazine component which is thought to be present in an undesirably high proportion in the mixture.