Flowlines, used to transport crude oil or process water in petroleum engineering, are nowadays typically made of steel. Thermoplastic polymer pipes offer a great potential to reduce installation costs by substitution of the steel pipes. While steel pipes are impermeable, polymer pipes might show reasonable permeation rates against hydrocarbons. Up to now, no data on application-relevant permeation rate of polymer pipes for oilfield applications are available. Therefore first application oriented permeation measurements were done by sampling the permeate in dis-tilled water. By means of extensive liquid/liquid extraction methods and gas chro-matographic quantification a time lag of about 4 weeks for toluene permeation through polyethylene-pipes (32mm/SDR11, PE100) was determined. Furthermore a permeation test device was designed and implemented to characterize the per-meation rate of 32mm-pipes systematically. Additionally a test setup for pipes, which are already in service, was implemented. By means of the novel test device the permeation rates of volatile organic compounds through the wall of PE-pipes were determined at 35°C and 3 bar inside pressure. An almost linear relationship between the concentration inside the pipes and the permeation rates, ranged from 70 mg/m²d to 1200 mg/m²d, was shown. The novel permeation test device for polymer pipes proved to allow the determination of the toluene-permeation both, in laboratory and in-situ. This master thesis is also a contribution in the ongoing development of the research field “permeation” at Polymer Engineering and Science Leoben.