A review of the large number of stratigraphically controlled isotopic age determinations relevant to the Triassic shows that the ages of the Triassic‐Jurassic and Permian‐Triassic boundaries are approximately 200 Ma and 245 Ma, respectively. Estimates for the period boundaries within the Triassic are as follows: Norian‐Carnian—215 Ma; Carnian‐Ladinian—225 Ma; Ladinian‐Anisian—235 Ma; Anisian‐Scythian—240 Ma. Because of the many uncertainties inherent in these estimations, both stratigraphic and radiometric, the ages of the Triassic system and stage boundaries given above are assigned an error of ± 5 Ma.