We were concerned about the precision (i.e., consensus as to meaning) of adjectives and adverbs used to express frequency in the medical literature. We asked 103 physicians and 106 nonphysicians to assign to each of 22 such modifiers a percentage representing their understanding of the term. As indexed by the standard deviations, the degree of imprecision for 17 terms was so great for both physicians and for laymen as to make their use unacceptable. Consensus was significantly less among laymen than among physicians for 10 of the terms. Greater consensus was shown by native English-speaking physicians than by those with other native languages. Our data suggest further that American graduates of American medical schools show more consensus than American graduates of foreign medical schools. Board-certified physicians did not show greater consensus than physicians who were not board-certified. Verbal expressions of frequency should be eliminated from medical communications; failing that, the author should specify numerically the frequency he intends when he uses any such expression.