A prolonged glucose loading test is described. When used in five patients with familial periodic paralysis it brought them into a state of massive hypopotassaemic paralysis at the first attempt, without the use of exogenous hormone. Three normal persons were subjected to the same glucose loading without exhibiting hypopotassaemia or muscular weakness. There were no essential differences in serum glucose levels between the two groups of individuals. The efficacy of previous methods of inducing paralysis, hormonal as well as non-hormonal, is reviewed, and the advantages of this new method are pointed out.