Multimorbidity is the coexistence of more than one chronic disease. Multimorbidity results in high health service use, competing demands on patients and health care professionals, reduced quality of life and higher mortality, with greater impact for Maori and Pacific people, and those living in deprived areas. Research focused on multimorbidity is scarce internationally and almost non-existent in New Zealand. The aims of the research project are to (1) describe the prevalence, patterns and impact of multimorbidity in New Zealand using routinely collected data; (2) understand and describe patients' understanding of, and experience of living with multimorbidity, using focus groups, in-depth interviews and a survey of patients with multimorbidity; and (3) develop interventions aimed at reducing the impact of multimorbidity in New Zealand, including identifying best clinical practice models, focused amendment of clinical guidelines, and identification of pro-equity interventions. Our aim is to improve health outcomes for patients with multimorbidity.