Evidence is growing that several computer-aided psychotherapy (CP) systems can effectively improve a range of common mental health problems. Most clients find CP acceptable because of its convenience, confidentiality, and reduction of stigma. CP can be accessed in a clinic, but recently clients have used CP especially on the Internet at home, with brief support on a telephone helpline and/or by email. Brief and efficient screening and support greatly reduce attrition. CP's efficacy, and encouragement of its dissemination and implementation by some national funding bodies and governmental agencies, has led to its spread as a regular care option and is increasing access to psychological therapies in some countries. Transfer of this new approach from use in tight research studies to use as an integrated part of everyday care under widely varying conditions generates teething problems that are being managed in diverse ways across different centers. Anonymized Internet audit of CP outcomes facilitates effective care and clinical governance. This review examines the current state of the art as well as the science and broad applications of CP.