This thesis contributes to the understanding of the effectiveness of marketing strategy making processes. It examines how such effectiveness is contingent upon the internal and external environments in which the process operates and, therefore, how the requisite process is contingent upon its organisational and market context. It builds on the fields of strategy content and strategy process and of organisational effectiveness, organisational culture and organisation theory. It tests and develops Burrell and Morgan’s congruency hypotheses as an explanation of the effectiveness of marketing strategy making processes. That work postulates that effectiveness results when the process is congruent with both its internal environment (i.e. microcongruent) and external environment (i.e. macrocongruent) This work takes a pragmatist epistemological perspective. The methodology is qualitative, using multiple-informant case studies. The congruency hypotheses are operationalised using a model and constructs based on the extant literature. The work is restricted to the medical products market in order to optimise insight and understanding. The findings support the congruency hypotheses. Strong strategy is associated with simultaneous macrocongruence and microcongruence. Further, a mechanism for the hypotheses is identified. Interactions between the strategy process and organisational structure, systems and habits provide an underlying mechanism of microcongruence. Failure or success of the process to manage market complexity and turbulence provide an underlying mechanism of macrocongruence. This work contributes to theory, confirming the congruency hypotheses, extending them into marketing strategy making and making a new contribution concerning the mechanism of congruency. To methodology, this work confirms the use of case studies, extends it to consider simultaneously internal and external environments and makes a new contribution concerning the construct of strategy quality. To practice, the work confirms the value of planning in complex markets, extends the concept of a “requisite” process and contributes new ideas for the deliberate management of marketing strategy making processes.