The research presented in this thesis arose out of work done by the Māori Asthma Review (Pomare et al, 1991). The Māori Asthma Review was undertaken because of concern regarding the excessive number of deaths and hospitalisations from asthma among Māori people, even though evidence at that time, was that asthma prevalence was similar between Māori and non-Māori children. One of the key findings from the review was that there were a combination of barriers for Māori when accessing asthma services, which were almost certainly reflected in more severe asthma and higher hospital admission rates. This thesis has involved conducting three pieces of new research: (i) a series of reviews and analyses of descriptive data on asthma prevalence, hospitalisations and mortality in Māori and non-Māori; (ii) analyses of the ethnicity data from the International Study of Asthma and Allergies in Childhood (ISAAC) Phase III Wellington survey; and (iii) a follow-up study of Māori adolescents with asthma examining factors affecting asthma severity, access to health care and asthma quality of life in this adolescent population. The mortality analyses showed that Māori were disproportionately affected by the asthma epidemics during the 1960s and 1970s and that while the asthma mortality rates have declined now, they remain higher in Māori than in non-Māori. Asthma hospitalisation rates continue to be higher in Māori compared to non-Māori across all age groups. Hospital admission rates are generally higher in rural areas for Māori whereas those for non-Māori are higher in urban areas. Analyses of the ISAAC Phase III data show that Māori children are experiencing both greater asthma symptom prevalence and increased asthma severity compared with non-Māori children and that this is not explained by risk factors such as smoking. In the follow-up study of Māori adolescents, baseline asthma severity and frequency of wheeze were important determinants of subsequent morbidity. Having an asthma action plan, a peak flow meter and having routine visits to the general practitioner were all associated with small improvements in asthma quality of life during the one year follow-up. The only significant predictor of access problems during the one year follow-up was having had access problems at baseline. Cost was the most significant barrier to accessing care for these families. Asthma continues to be a significant health problem for Māori. The research conducted for this thesis supports and extends previous research indicating that asthma is more severe in Māori, because of problems of access to health care. It also indicates that differences in asthma prevalence between Māori and non-Māori are now being seen in children as well as adults, and that management and treatment issues underlie the emerging increase in asthma prevalence among Māori. Attention to access issues across mainstream health structures along with support for Māori provider organisations should continue. Additonally, active approaches to monitor differential treatment and barriers to effective interventions are needed.