Strategies to retain participants in a long-term HIV prevention randomized controlled trial: lessons from the MINTS-II study.

Achieving satisfactory retention in online HIV prevention trials typically has proven difficult, particularly over extended timeframes. The overall aim of this study was to assess factors associated with retention in the Men's INTernet Study II (MINTS-II), a randomized controlled trial of a sexual risk reduction intervention for men who have sex with men. Participants were recruited via e-mails and banner advertisements in December, 2007 to participate in the MINTS-II Sexpulse intervention and followed over a 12-month period.