AIMS AND METHOD: Modern mental healthcare providers must demonstrate service-level clinical effectiveness to key stakeholders. We introduced two performance indicators of clinical effectiveness based on outcome data from routinely collected Health of the Nation Outcome Scales (HoNOS) and HoNOS-secure assessments across St Andrew's Healthcare, a charity providing in-patient services in Northampton and Essex. We present outcome data from the period 2004-2007. RESULTS: The indicators showed consistent 90-day improvement rates and increasing stability over time. The validity of results is supported by levels of change along predicted lines among different patient cohorts. CLINICAL IMPLICATIONS: It is possible and beneficial to use routine outcome measures to demonstrate clinical effectiveness at service level. The future of managing mental health outcomes will be in electronic health records systems.