Several upper mantle velocity distributions in western Canada are determined from short-period (1--10 Hz) body wave (P) observations. With the use of quantized ray theory, synthetic seismograms were constructed for laterally homogeneous earth models to satisfy the absolute travel time of first arrivals and the differential travel times and relative amplitudes of later arrivals. On the basis of travel time and amplitude observations, three models were obtained that correspond to three different regions. All of the three models show the presence of a low-velocity zone and discontinuities at 410 and 650 km. Of the three models, models WCA and WCB show the presence of a discontinuity in slope at about 504 km, but this is absent in the model WCC. Models WCA and WCB differ in their thickness of the lithosphere, the absolute velocity below the base of low-velocity zone, and the gradient of the velocity between the base of the low-velocity zone and 300 km of depth. Beyond 300 km, models WCA and WCB have the same velocity distribution. An extremal inversion determination of the depth limits to the discontinuities at 410 and 650 km indicates a maximum uncertainty of about ¿30 km in depth to the discontinuities. An analysis of reduced delay times for the reflection from the 410-km discontinuity indicates a local down-buckling of the 410-km discontinuity by 30 km under the Cordillera.