The potential risk to hearing that mass-storage personal listening devices (PLDs) pose remains unclear. Previous research in this area has either focused on maximum outputs of these devices or on ear-canal measurements of listening levels that could not be compared to standards of occupational noise exposure. The purpose of this study was to compare two standard measurement protocols [ISO 11904-1 (2002), Switzerland; ISO 11904-2 (2004), Switzerland] for the measurement of preferred listening levels of PLD. Noise measurements, behavioral thresholds, and oral interviews were obtained from 30 (18-30 years) PLD users. Preferred listening levels for self-selected music were determined in quiet and background noise using a probe microphone, as well as in the DB-100 ear simulator mounted in KEMAR. The ear-canal measurements were compensated for diffuse-field. Only one of the subjects was found to be listening at hazardous levels once their reported daily usage was accounted for using industrial workplace standards. The variance across subjects was the smallest in the ear-canal measurements that were compensated for diffuse-field equivalence [ISO 11904-1 (2002), Switzerland]. Seven subjects were found to be listening at levels above 85 dBA based on measurements obtained in the KEMAR and then compensated for diffuse-field equivalence.