Model calculations show that channeling may have a detrimental effect on radionuclide transport because fast channels may carry some of the mass of the radionuclides considerably faster than the average flow would and may give this portion considerably less time to decay. Channeling further aggravates the retardation of the sorbing nuclides because less surface area is available for sorption in a channel within a fracture than if the whole fracture is exposed to the flowing water. An ongoing experiment in the Stripa mine aims at studying some aspects of channeling. A special packer of a new design is used. Preliminary results show that there is uneven flow in the fractures which indicates channeling.