Given its importance to institutions, policy-makers and intending students, there is a surprising lack of research exploring the reasons students choose to undertake a research degree. What studies there are tend to be largely descriptive and the topic lacks a theoretically-informed framework through which student decisions can be examined and comparative work developed. We outline such a framework drawing on self-determination theory and social cognitive career theory. Our framework comprises five categories: autonomy; relatedness; competence and self-efficacy; outcome expectations; and goals. To assess its utility, the framework is used to interrogate data generated through a series of focus groups involving PhD students studying in Australia in the area of information and communications technology. The framework proved capable of organizing data in a robust, comprehensive and coherent way.