A protocol for the use of vitamin C in the treatment of cancer, developed over a number of years in Vale of Leven Hospital, Scotland, is presented. Clinical experience has shown this protocol to be both safe and efficient. It need not be followed 'to the letter', but provides general guidance to physicians unfamiliar with this therapeutic approach. It recommends that all cancer patients treated in this fashion be given an initial course of intravenous ascorbate followed by a maintenance oral dose to be continued indefinitely thereafter. The importance of continuous as opposed to intermittent administration is emphasized.