This thesis on the management of the accounting systems in the mergers-acquisitions rests on the survey of twenty-two operations of mergers-acquisitions achieved between 1992 and 2007 by four groups, quoted or no, operating in different sectors (distribution, wines and spirits, champagne, steel industry). The analysis of the data is done while using the cognitive mapping for the interviews and the chronological matrix for the other introverted data (direct observation, study of in-situ documents and external). The results show the differentiated approaches and non linear according to the groupspurchasers. While being inspired by the acculturation models, a double typology of the determinants and the consequences of the accounting systems integration in every studied group and a general model has been elaborated while distinguishing four logical of integration: the absorption, the separation, the reversed partial adoption and the combination. From this model we count features of the accounting systems integration in the four studied groups while isolating the explanatory factors and the consequences in every logic of integration. Then, we construct a typology of the accounting systems integration in the mergers-acquisitions while putting little in evidence the predominant explanatory factors as the fashion of management or very centralized more or less of the group purchaser and the level advanced of the accounting systems of the grouppurchaser and the enterprise acquired. To the level of the consequences, the adaptation more or less voluntary of the salaried employee to the proposed organizational changes either imposed by the group purchaser detaches himself strongly except in the logical separation where these changes appear like miners insofar as the teams in place and themethods of work are maintained.
