The use of tissue culture techniques for the international movement of potato clonal germplasm was studied. "Multi-meristem" cultures were established from virus-free plants by procedures described earlier by the authors. Well developed plantlets, regenerated aseptically from "nodal cuttings" of shoots produced in multi-meristem cultures, were used for international transfer. The medium contained the Murashige-Skoog mineral and vitamin components, with 2% sucrose, and was supplemented with 2 mg/l calcium pantothenate and 0.2 mg/l gibberellic acid. The cultures survived the mail shipment when 1% agar medium and small test tubes were used; polystyrene containers reduced damage due to abrupt temperature changes. At the receiving end, higher survival rates during the recovery of plants was achieved through potting of plantlets regenerated from nodal cutting cultures. A total of 43 pest and disease-free potato clones have been distributed in vitro from CIP to 10 different countries. The training of technicians from developing countries played an important role in the application of these methods. © 1979 Springer.