This paper combines the recent measurements of P and S wave travel times from intra-plate earth-quakes with travel times from deep-focus earthquakes reported earlier to infer the velocity structure of the mantle. It is reasonable that the source bias for intra-plate earthquakes is less pronounced than that for other shallow-focus earthquakes such as those occurring in island arcs. The inclusion of intra-plate earthquakes compensates for the lack of uniform areal distribution exhibited by the deep-focus earthquake data and augments the number of high quality travel time observations. The features observed in the variation of telesesismic travel times from intra-plate earthquakes are consistent with the travel time variation determined from deep-focus earthquakes (especially the P wave travel time variation). The combined intra-plate and deep-focus earthquake travel time data were converted to determine an average (spherically symmetric) compressional and shear velocity model and, subsequently, a three-dimensional compressional velocity model for the earth's mantle. Lateral variation in the mantle accounted for most of the scatter in the observed P wave travel times. The average compressional velocity model suggests two rapid velocity increases at 500 and 670 km depths and a small velocity gradient in the depth interval of 100--450 km. The 3-D model determined from the augmented travel time data set corroborated the earlier findings (1) that the lateral heterogeneities are more pronounced near the upper-mantle and near the core-mantle boundary and (2) that the surface tectonic features are correlated with compressional velocity anomalies near the upper mantle, but not with velocity anomalies below the upper mantle.