Online health communities provide a means for patients and their families to learn about an illness, seek and offer support, and connect with others in similar circumstances. They typically mix expert and peer interaction, using various collaborative technologies. Their advantage over static health websites is the richness of the interaction that is possible. The effectiveness of online health communities is based on a number of factors, including appeal, branding, and cultural competence. This presentation covers what online health communities are, the factors that make them successful, and the relevance to other forms of online education and support.