Although membrane filtration is an accepted technology in water treatment and in the dairy, food and beverage industries, membrane-based separations are relatively new for the chemical industry. Therefore, for a major part of these techniques, there is still a long way to go to make them truly attractive as an alternative to distillation, absorption and adsorption or extraction. However, the improvement potential in large-scale processes is enormous. In this paper, we present four different successful implementations of membrane-based separations in our chemical company, ranging from upgrading of a process gas stream in a bulk chemical process to recovery of enzymes in a fine-chemical process,The technical-economical aspects of these projects are discussed. The approach for implementation strongly differs depending on the existing situation in the plant. Replacement of existing separation units by more efficient membrane units quite often appears economically unattractive, whereas in new installations or debottlenecking situations, membrane separations have a better chance of success. Reliability and durability are key criteria in the process industry. Therefore, it should be strongly recommended that a large-scale data base be created, e.g. by proper demonstration projects. Some general conclusions are presented concerning recommended directions in the future development of membrane technology.