The place of English language instruction in Māori-medium programmes is a controversial issue. Many Māori-medium schools either exclude it from their curriculum, or pay lip service to it. However, English language instruction is an important element for all Māori-medium schools to consider, as its role will affect the extent to which the students achieve the aim of becoming biliterate. Unfortunately though, how to support the English language growth of Māori-medium students remains an as yet unresolved and under-researched issue. It is this theme that this research seeks to investigate. This Doctoral thesis reports on a multiple case study research project that investigated the English transition programmes of three Māori-medium schools including: a wharekura, a kura kaupapa Māori and a bilingual school. The research implemented a Kaupapa Māori framework and used interviews, classroom observations, and language assessments to explore the subject. The central aim of this project was to examine how these schools arrange their English transition programmes, what issues they face, and how they negotiate them. This research found that the teaching of English in Māori-medium education is an area in which Māori-medium schools have little support, and often struggle to negotiate. Despite this, some programmes offer good quality instruction that contributes to their students achieving high levels of literacy development. This study concluded that there is a relationship between the English transition programme design, and the students’ literacy (English and Māori) development. The higher quality programmes included greater quantities of English instruction, the staff was informed about bilingual education principles and they nurtured closer relationships with their student. Overall, this research found that English language instruction can play a part in Māori-medium education in a way that does not need to detract from the school focus on the learning of te reo Māori. The layout of this thesis is as follows. Chapter One explores the history of research into bilingualism before discussing some of the theoretical models that apply to this research project. Chapter Two explains some of the structural considerations concerning bilingual programmes, and the characteristics of Māori-medium education in the New Zealand context. Chapter Three examines New Zealand research into Māori-medium education with a particular focus on three areas: general teaching practices, research about student assessment, and research about English transition. Chapter Four discusses the methodological decisions that I made when approaching this research and the research tools I chose for the data collection process. Chapters Five, Six and Seven each presents a single case study of an English transition programme in a Māori-medium school. They provide descriptions of the programmes and explore the perspectives of the key participants, including staff and students. An analysis of Year 8 student literacy outcomes are provided followed by a discussion of the predominant findings that emerge. Chapter Eight is the discussion chapter where the key results from all three case studies will be discussed. This is followed by the concluding chapter (Chapter Nine), which discusses the educational implications of this research.