Objectives. This study assessed the differential effects of face-to-face interviewing and audio-computer assisted self-interviewing (audio-CASI) on categories of questions.

Methods. Syringe exchange program participants (n = 1417) completed face-to-face interviews or audio-CASI. The questionnaire was categorized into the groups “stigmatized behaviors,” “neutral behaviors,” and “psychological distress.” Interview modes were compared for questions from each category.

Results. Audio-CASI elicited more frequent reporting of “stigmatized behaviors” than face-to-face interviews. Face-to-face interviewing elicited more frequent reporting of “psychological distress” than audio-CASI.

Conclusions. Responding to potentially sensitive questions should not be seen as merely “providing data,” but rather as an activity with complex motivations. These motivations can include maintaining social respect, obtaining social support, and altruism. Ideally, procedures for collecting self-report data would maximize altruistic motivation while accommodating the other motives.