Valid measures of nausea are needed to evaluate the various treatments used to counter the nausea produced by chemotherapy. The overall nausea intensity (ONI) produced by 17 chemotherapy drugs was estimated by 17 physicians and 8 nurses, and 25 patients undergoing chemotherapy described the subjective qualities and ONI of their nausea on a modified form of the McGill Pain Questionnaire. The scores for the affective and miscellaneous categories of words in the questionnaire were found to correlate significantly with the physicians' and nurses' ONI estimates. The results formed the basis for the Nausea Questionnaire, which provided three indices of nausea: a nausea rating index (NRI), ONI and intensity of nausea according to a visual analogue scale (VAS). All three indices correlated significantly with the physicians' and nurses' ONI estimates and were significantly intercorrelated. All three also provided significant differences when the scores of patients who had received cisplatin or 5-fluorouracil were compared. The results indicate that the Nausea Questionnaire provides three valid indices of the subjective experience of nausea.