Irradiated nuclear fuel has been stored in water pools at essentially all nuclear reactors, beginning with the earliest plants in 1943. Fuel from water-cooled power reactors is clad either with Zircaloy or with stainless steel. Zircaloy-clad fuel has been stored in the U.S. pools since 1959. Some experimental stainless-steel-clad fuel was stored for 12 yr in the U.S. before reprocessing. Canadian Zircaloy-clad fuel has been stored since 1962. There has been no evidence that the fuel has degraded during pool storage, based principally on visual observations and radiation monitoring of pool air and water. However, several fuel rods have been subjected to metallographic examination after pool exposures up to 11 yr, also with no evidence that the fuel cladding has degraded in the pool. Canadian fuel stored up to 10 yr was returned to a reactor and performed well. Favorable storage experience also has been indicated for other countries with fuel residence times of 5 to 10 yr. Fuel that developed defects in the reactor generally does not require special storage procedures in U.S. experience, although bundles with broken rods have been canned for shipment. In some countries, all defective fuel is canned. Mechanical damage during fuel handling has been minor. The pool storage environment is high-purity water at 5.3 to 7.5 pH, except for pools for pressurized water reactors, which utilize boric acid pool chemistry at 4.5 to 6.0 pH. Pool water temperatures generally range between 20 and 50°C. The favorable storage experience, demonstrated technology, successful handling of fuel with reactor-induced defects, benign storage environments, and corrosion-resistant materials offer sufficient bases to proceed with expanded storage capacities and extended fuel storage until questions regarding fuel reprocessing and final storage of nuclear wastes have been resolved. Some surveillance is justified to detect degradation if it becomes significant. Surveillance programs are already under way in several countries.