This article attempts to underline the instability of the professionalization processes within two segments of the accountancy profession. These segments are facing with the necessity of redefining their professional field in a context of changing markets and products but also of reform of the profession which relaunches conflicts of territories and of legitimacy. It is based on the compared analysis of two case studies, the one in an office of chartered accountancy, the other one in an association of management and accounting services. It accounts for their strategies for protecting or conquering territories, it underlines their limits and their unpredictable character facing the actors’ games which result from them.