Researchers have attempted to reach MSM for HIV prevention research and intervention on the internet. In the past 10 years, there has been a proliferation of internet surveys and HIV research studies among men who have sex with men that utilize the internet for data collection and, in some cases, the delivery of HIV prevention content. The development of internet-based interventions has been recently identified as especially promising because of its potential for scalability. However, there are also important limitations to internet-based data collections and prevention studies. The most important of these relate to representativeness and opportunities to introduce bias to data collections and differences in access to and use of internet among different subgroups of MSM. Equally important, although less discussed, are the unique ethical and human research protections challenges posed by online sexual health prevention studies.