<p>Over the past 50 years there have been many innovations in New Zealand's mental health services. Using case study methodology this research examined two innovations involving general practice - the Newtown Union Health Service (NUHS) mental health programme and the Hawke's Bay (HB) shared care pilot - targeted at people with serious and ongoing mental illness (SOMI). The intent of the research was to inform service delivery arrangements and to provide new knowledge concerning the development of innovative services. Four sources of data - programme documentation, evaluation reports, utilisation data and stakeholders' experiences acquired through questionnaires and interviews - were used in developing the case studies. While the history of these innovations was traced to specific actions, these innovations emerged because of the national and clinical context. The NUHS programme was a bottom-up development the innovation occurring because NUHS needed to find a way of meeting the needs of the people with SOMI who were registered there. NUHS practitioners in consultation with the community made decisions concerning the programme's development The HB pilot was a top-down development that was purchased because new money became available. Primary and secondary service practitioners, managers, researchers and the purchaser made decisions concerning the pilot's initial development. The factors that shaped the innovations included: funding, staffing, clinical and financial risk management and time. Similarities in the innovations included the range of arrangements for mental health care for individual people (from GPs being the sole providers through to GPs providing only physical health care, with the mental health service providing the mental health care), issues of trust and poor communication between the primary and specialist services and the frequency and length of consultations. Differences included the payment arrangements, access issues, the formalisation of co-ordination arrangements and the role of the nurse. The research found that to be adopted for routine use these innovations needed to develop effective service delivery arrangements. The NUHS programme was more successful than the HB pilot at delivering accessible, acceptable, co-ordinated, comprehensive, efficient and effective services. The findings regarding targeting, funding mechanisms, practitioner roles and the time it takes for trust to develop so that innovative services can become established have implications for Primary Health Organisation development. Research is needed on other innovative services to establish whether evaluating the effectiveness of the service delivery arrangements provides a useful framework to monitor and guide the implementation of an innovation in service delivery.</p>