Planning, construction and commissioning of a manufacturing plant constitute one of the most demanding and interesting areas of biotechnological production. Each plant is custom‐made and designed individually to accommodate the projected demands of the company. The challenge is to find the compromise between functionality and flexibility, on the one side, and the financial constraints as to capital investment and operating costs, on the other. This chapter introduces the principles of an investment project, and starts with an explanation of the phases of the planning, construction and commissioning process. It discusses typical time schedules of engineering projects, and elaborates on cost estimates. Since engineering projects are usually executed with specialized external engineering companies, the chapter focuses on how to build and maintain contractual relationships. The chapter explains the success factors for the execution of an engineering project, and also deals with the legal framework for the construction of an industrial plant.