The Shell HYCON process converts high sulphur, high metal content vacuum residues into atmospheric and vacuum distillates. The HYCON process is equipped with catalyst bunkering facilities that make on-line catalyst replacement possible. The first unit was built at the Shell Pernis refinery and was started in 1989. The process performance (in terms of sulphur/metals removal and conversion into distillates) is in line with predictions, and the catalyst bunkering system works well. During the start-up phase of the Pernis unit, equipment and materials problems were encountered. These problems were solved by repairs and replacement of the affected equipment. At present, the throughput has been increased to well above design value and a high conversion of vacuum residue into distillates has been consistently achieved.