Hellroaring Creek Stock intrudes rocks of the Precambrian Purcell Supergroup which crop out in southeastern British Columbia. Previous K–Ar measurements (Lowdon 1961) indicated a minimum age of 700 m.y. for this stock. Present Rb–Sr isotope measurements indicate an approximate age of 1260 m.y. Cleavage in the contact aureole of the stock indicates a structural event prior to intrusion.