[en] Proceedings of a workshop are summarized to identification of major technical concerns associated with in situ testing for nuclear waste isolation. The apparent needs and suggested in-situ testing programs identified during the workshop tended to concentrate on those parameters related to nuclide migration or, conversely, nuclide containment. As a generalization, the workshop agreed that a definition of the source term, including waste form (age, chemical composition, isotopic composition, and packaging), canister material, and overpack and/or backfill material, was lacking. This lack of information introduces constraints on the discussion of many of the topics included, especially near-field and waste/rock interactions. Additionally, it was felt that chemical and mechanical behavior in the near-field environment was not well understood and that in-situ testing and demonstration projects would be necessary. In most instances, investigations relating to source term and near-field interactions would require the development of coupled research programs including components of analytical modeling, laboratory testing, in-situ testing, and demonstration for public acceptance. In the far field, the primary issue of concern was the characterization of the hydrogeologic environment, because of the need to assess nuclide migration phenomena. As a generalization it was concluded that because of the time frame under consideration and the scale of the repository, specific in-situ testing should be directed toward computer model verification and evaluation of scaling problems. It was also suggested that evaluation of time and geometric in-situ phenomena occurring naturally should be pursued in order to better assess scale and time factors