Purpose: The paper seeks to identify the quality characteristics of critical action research and action research theses compared to traditional research thesis writing. Design/methodology/approach: Drawing on the literature and the authors' experience with supervising and examining action research theses, the paper identifies key problem areas in the literature and suggests effective strategies for meeting these challenges and avoiding pitfalls through reflective practice and questioning insight. The paper includes sets of crucial questions for higher degree students to address. Findings: The paper presents definitions of and checklists for quality action research, a quality thesis, and a quality action research thesis. It also presents two conceptual models that illustrate the differences between the "research" and thesis "writing" activities and processes in general, and the collaborative core action research in the fieldwork and the critical action research thesis that needs to be the candidate's independent contribution to knowledge in theory and practice. Originality/value: The definitions, checklists and conceptual models will be useful to postgraduates, supervisors and examiners of action research theses, because they clarify for them the similarities and differences between a traditional thesis in the social sciences and a thesis by action research. (Contains 2 figures, 1 table, and 3 notes.)