Subjects’ estimates of the frequency of occurrence of the letters of the alphabet were compared with previously reported letter-frequency counts. The results indicated an overall good relationship between actual and judged rank, but there were consistent letter-specific under- and overestimations. These inaccuracies were not accounted for by letter versatility, first-position frequency, or order in the alphabet. There was evidence that subject-derived estimates of letter frequency were somewhat better predictors of reaction time performance on letter-processing tasks.