Loudness balances were collected from 3 subjects, employing 57 combinations of 13 frequencies extending from 20 to 5000 cps. Determinations were made from levels close to threshold to the highest levels tolerable by the subjects, with 5-dB intervals. Stimuli were applied by an earphone through individually moulded ear inserts, and were measured in decibels sound-pressure level a few millimeters from the eardrum. For each subject, a symmetric and transitive subset of the data was employed for construction a set of matching functions and a set of equal-loudness contours. Matching functions generally were linear, or showed a double inflection (in log-log coordinates) Equal-loudness contours generally agree with previous determinations, but show a steeper rise towards low frequencies; below 300 cps, and at medium levels, the contours approach straight lines with a slope of 40 dB/decade. Obtained matching functions are compared to 3 sets of theoretical functions, favoring the matching functions derived from loudness theories developed by Zwicker and by Zwislocki.