At the time of writing this thesis, outsourcing has become a daily political issue so I decided to write about my experience regarding this topic including my company K.S.T. TRGOVINA d.o.o. The company is providing cleaning services to wide range of customers. I wrote about necessity of externalization process in the public sector which results in reducing costs and increased efficiency. This is preceded by a general part on outsourcing: the definition and concept development, the objectives, the process of implementation of outsourcing, and advantages and disadvantages of outsourcing in Croatia. The paper describes the strategic benefits of outsourcing as a tendency which strongly influenced changes in the organization compare to classical company and has become a fundamental strategy of restructuring the organization with the purpose of having competitive advantage. Scientific and technical papers were used when writing this thesis that have the outsource topic, business strategy and management systems included. When describing experiences of K.S.T. TRGOVINA d.o.o., data from the business records of the Company and tender documentation and reports of the Central Office for Public Procurement are used.