We evaluate the impact of a videotape specially produced to supplement written information about preventive HIV vaccine trials. One hundred eighty-six injection drug users were randomly assigned to an education session in which either: (a) a pamphlet was reviewed before a brief discussion period or (b) the videotape was watched prior to reviewing the pamphlet and participating in the discussion. The relationship among retention of information, trust in government, and willingness to participate in a vaccine trial was tested before the presentation of information, immediately after, and 1 month later. Results indicate that both methods produced significant increases in knowledge immediately after information presentation, but only the video-supplemented group retained the information 1 month later. Subjects receiving the video supplement also showed a significant increase in trust at the first posttest period, but this increase was not maintained 1 month later. Regardless of group assignment or evaluation point, willingness to participate was not associated with knowledge but was associated with trust in government.