A programme is an instrument for education. Through educational programmes we help shape our society. Programme design includes decisions on what society finds valuable for people to learn, and how this should be structured and organised. In this way it influences teaching and learning. Therefore understanding how and on what basis programme design decisions are made is vital for the improvement of teaching and learning. Yet, there is a dearth of research that provides this understanding in the context of tertiary education. This thesis alleviates this scarcity by describing the theorising of design practice of certificate and diploma programmes in a polytechnic in Aotearoa/New Zealand. The research presented in this thesis consists of an interpretive case study of a polytechnic in Aotearoa/New Zealand. The study included embedded case studies of programme design practice at institutional level and of design practice of five certificate and diploma programmes across the polytechnic. Data were analysed from 32 interviews with representatives of the six embedded cases, from documents including the institution’s Academic Statute, its Quality Management system and approved programme documents, and from observation of one meeting. The findings show that programme design practice can be observed through various lenses. For this case study the following seven lenses were identified: 1) The teaching and learning lens shows how language shapes the conceptualisations of a programme and how these conceptualisations relate to views on teaching and learning; 2) The rational lens shows how models and frameworks influence programmes, how these models and frameworks become rationalisations that are often used unconsciously, and what the implications of this are; 3) The cultural lens allows exploring what is considered normal within programme design practice and indicates how differences from the norm are being approached; 4) The personal experience lens highlights how the personal experiences of people involved contribute to programme design considerations and decision-making; 5) The ethical lens investigates how people’s moral and professional responsibilities influence their programme design practice; 6) The business lens illustrates the contribution of business considerations to programme design; and, 7) The social-political lens highlights how people’s formally and informally assigned roles and responsibilities, their political responsibilities, and their negotiations between multiple responsibilities impact on programme design practice. The images of these lenses are interrelated. To create a comprehensive understanding of the images and their interrelationship, a programme has been theorised as a complex system. The constituents of this system are people’s considerations, language, silences, experiences and relationships. These constituents only concern those aspects of education that are assigned to the concept of ‘programme’. For the current case study these aspects were found to consist of six components: consultation for and development of a programme; intentions; structure and instruction; administration and management; assessment; and evaluation of a programme, including elements within these components. The people who create the considerations, language, silences, experiences and relationships were found in this case study to be people within the polytechnic. The complex programme system interacts with the outside world. Programme design practice then is the programme system’s adaptation to influences from outside. Ideological discourses are shown to form the power structures that shape the direction of adaptation of the programme system. For this case study the analysis of the images of the seven lenses and their interconnections shows neo-liberalist discourses as the prevailing ideological discourses determining the direction of adaptation of the complex programme system. The findings of this study have three major implications for practice. Firstly, the effects of a programme on the world around it cannot be predicted or controlled but emerge from the programme system. Secondly, the findings imply that if a programme is to survive or continue to develop, it needs diversification. Further strengthening of the already dominant ideological discourses directing programme systems in the context of this case study risks the death of these systems. And thirdly, acknowledging ideological discourses as the power structures that shape the direction of the adaptation of complex programme systems requires practitioners to be responsible in deciding which discourses to follow and to be mindful of the possible implications of their decisions.