Yves Jung, Pascal Ballester, Klaus Banse, Wolfgang Hummel, CarloIzzo, Lars K. Lundin, Andrea Modigliani, Ralf M. PalsaEuropean Southern ObservatoryDerek J. McKayRutherford Appleton LaboratoryMichael KiesgenMichael Bailey Assoc.Cyrus SabetTekom GmbHAbstract. Since the beginning of the VLT operations in 1998, substan-tial effort has been put in the development of automatic data reductiontools for the VLT instruments. A VLT instrument pipeline is a com-plex system that has to be able to identify and classify each producedFITS file, optionally retrieve calibration files from a database, use animage processing software to reduce the data, compute and log qualitycontrol parameters, produce FITS images or tables with the correct head-ers, optionally display them in the control room and send them to thearchive. Each instrument has its own dedicated pipeline, based on a com-mon infrastructure and installed with the VLT Data Flow System (DFS).With the increase in the number and the complexity of supported instru-ments and in the rate of produced data, these pipelines are becomingvital for both the VLT operations and the users, and request more andmore resources for development and maintenance. This paper describesthe different pipeline tasks with some real examples. It also explainshow the development process has been improved to both decrease its costand increase the pipelines quality using the lessons learned from the firstinstruments pipelines development.1. IntroductionThe VLT instruments pipelines development, integration and maintenance aretasks under the responsibility of the Data Flow System (DFS) group at ESO.Seven operational instrument pipelines (ISAAC, FORS1, FORS2, NACO,UVES, FLAMES, VINCI) are currently under maintenance, and seven othersare being developed and are due over the next two years (CRIRES, VISIR,764