Oxygen, hydrogen and carbon isotopic analyses of rocks from the Canadian Cordillera document regional variations in the origins and evolution of crustal fluids. High temperature systems in unmetamorphosed, felsic volcanic rocks are characterized by low Δ18O values. Veins in regional metamorphic rocks are characterized by Δ18O values that reflect approximate oxygen isotopic equilibration of the fluids with regional rock units. The Δ D studies indicate that both systems were dominated by meteoric water. The Δ13C values for vein carbonate indicate a regional lithologic control on Δ13C values. The data indicate that convection of surface fluids to depths of 10 or more kilometers during orogenesis was common. The existence of deep convection cells involving meteoric water further indicates that fluid pressures to these depths must have been approximately hydrostatic. Regional structural style appears to exert an important control on the depth of penetration of surface fluids. ¿American Geophysical Union 199