We describe the development process and completed structure, of a self-help online intervention for bipolar disorder, known as MoodSwings ( www.moodswings.net.au) . The MoodSwings program was adapted as an Internet intervention from an efficacious and validated face-to-face, group-based psychosocial intervention. The adaptation was created by a psychologist, who had previously been involved with the validation of the face-to-face program, in collaboration with website designers. The project was conducted under the supervision of a team of clinician researchers. The website is available at no cost to registered participants. Self-help modules are accessed sequentially. Other features include a mood diary and a moderated discussion board. There has been an average of 1,475,135 hits on the site annually (2008 and 2009), with some 7400 unique visitors each year. A randomised controlled trial based on this program has been completed. Many people with bipolar disorder are accepting of the Internet as a source of treatment and, once engaged, show acceptable retention rates. The Internet appears to be a viable means of delivering psychosocial self-help strategies.