[en] Hundreds of kg of tritium have been released to the environment during the nuclear era. Two chemical forms predominate, tritiated water (HTO) and tritium gas (HT and T₂). Scientific utility has been gained from these releases in the fields of atmospheric chemistry, meteorology, oceanography and hydrology. The results are improved estimates of global tritium burdens, of atmospheric and oceanic circulation and mixing processes, and of hydrogen chemistry in the atmosphere. The inventory of HTO in the oceans was estimated to be 1.6 GCi at the end of 1972. The lower stratosphere of the Northern Hemisphere contained 2.5 MCi of HTO in mid-1979, with probably a similar amount in the Southern Hemisphere. The global Ht inventory is ca. 9 MCi. Utilization of the present environmental levels for tracer studies requires analytical sensitivities below 0.1 pCi/g. Quantity distribution of T₂-illuminated watches is expected to complicate environmental sampling operations, since they typically emit tens of nCi of HTO and lesser amounts of HT daily