The focus of this dissertation is on the good practices research and the critical success factors for merging and acquisition processes, used as basis for a critical analysis of the purchasing integration processes of two companies from the pharmaceutical sector. Since the birth of the first industries, this sector has had many historical negotiations in the merging and acquisitions processes. The paper describes and analyzes the main activities of purchasing and the technologies used by the acquiring company, which were defined as standards in integrating businesses. In order to have a throughout analysis, other complementary subjects were analyzed. They were of great importance for the overview of the integration process such as: motivational aspects used on merging companies, the functional detailing of the purchasing process and the supporting information technology. An analysis correlating the theory with real practices was done to verify their similarities. The conclusion took in consideration the merging processes review with suggestions for next studies and researches in the area.