Fifteen years ago we proposed that the diagnosis and treatment of sexual and other problems could be delivered in a professional and expert manner using personal computers. We programmed a sex-expert diagnostic and treatment system and tested it on several hundred individuals and couples in the laboratory, as well as on a pre-Internet regional computer network. Although the results of our studies were very encouraging, a lack of scientific interest at the time prevented further research being undertaken. Recently, the growth of the Internet has lead to the development and use of a number of online approaches to the delivery of psychotherapeutic services in general, and of some new approaches to sex therapy in particular. However, a number of scientific and professional issues need to be investigated if the public health potential of the provision of online psychotherapy services is to be realized. 617