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Of the different types of visual analogue and graphic rating scales tested in a series of experiments, only two were satisfactory: these were the visual analogue scale and the graphic rating scales used horizontally with the words spread out along the whole length of the line. Other types of scale used gave distributions of results which were not uniform. Unusual distribution of results occurred when patients selected a position adjacent either to descriptive terms or preferred numbers. In some experiments, the distribution of results was determined by the nature of the experiment. Alternation of the ends of a scale did not affect the results. The behaviour of the graphic rating scale was different in patients accustomed to completing it and in those not so accustomed.The results of pain severity measured by these methods showed a very good correlation with pain severity measured by the simple descriptive pain scale. Changes in visual analogue scores also correlated well with changes in simple descriptive pain scores. The visual analogue and graphic rating scales were more sensitive than the traditional simple descriptive pain scale. Most patients could readily use visual analogue and graphic rating scales despite having no previous experience. The failure rate was slightly lower with the graphic rating method. Use of these scales is the best available method for measuring pain or pain relief.