The New Zealand Primary Health Care Strategy states that quality primary health care is the first level of contact with the health system and should be universally accessible. Effective primary health care is an essential component of health systems, and is associated with more equitable distributions of health outcomes. However, not all New Zealanders have ready access to primary health care. For instance, adult residents of the Waikato region, and in particular Māori, have higher levels of unmet need for primay care than others. Improving the spatial equity of health services is a key step in achieving health equity. Health systems should contribute to achieving health equity and maintaining sustainable and equitable services into the future. This thesis research examines the spatial equity and sustainability of general practitioner (GP) services in the Waikato DHB region, using a mixed-methods approach to identify not only where inequities exist, but why they occur. A conceptual framework establishes a foundation for examining spatial equity and sustainability in New Zealand. Next, a systematic literature review identifies common definitions and measures of spatial equity. Primary Health Organisation (PHO) enrolment data is used to examine patterns of patient enrolment at GP services, and a range of health needs indicators were assessed for their suitability in the New Zealand primary care context. These findings inform the development of a Geographic Information Systems (GIS) model of spatial accessibility that is tailored to the Waikato District Health Board (DHB) context. The GIS model is then used, in combination with in-depth qualitative interviews, to examine the spatial equity and sustainability of GP services in the Waikato DHB region. Key findings include that spatial equity is commonly defined as a ‘need-based distribution of resources’, which can be quantified using a range of statistical and geospatial measures and techniques. PHO enrolment analysis revealed that most patients do not enrol with their closest service, and that the size of the ‘catchment area’ served by GP clinics varies with rurality. Analysis of indicators of health need suggest that ‘Ambulatory Sensitive Hospitalisations’ are a robust indicator; however, area-level socioeconomic deprivation is also strongly associated with other indicators of need and data is more widely available to researchers. Mixed-methods analysis suggests that GP services are not distributed equitably within the Waikato DHB region and that key barriers to access include the affordability, appropriateness, and availability of services. New Zealand’s history of colonisation and discrimination are identified as fundamental drivers of health inequity. Furthermore, population growth and ageing suggest that current levels of access to GP services are unlikely to be maintained in the future, while participants identify key economic, professional, organisation, and social dimensions that influence service sustainability in New Zealand.