Pcp arrival times reported to the International Seismological Centre (ISC) are inverted for vertical travel time anomaly at the core-mantle boundary (CMB). We first invert about 2¿106 ISC first P arrival data for the three-dimensional (3-D) structure of the mantle and hypocenter locations iteratively. The Pcp data are corrected for the relocated hypocenters and the 3-D structure. This correction has reduced the observed Pcp residuals. The corrected Pcp data are then inverted for the vertical travel time anomalies at the CMB, which are due either to velocity anomaly or topographic anomaly. The spherical average of the inverted structure requires either a velocity reduction in the boundary layer just above the CMB (by ~3% if the layer is 20 km thick) or a lowering of the CMB by 3 km. The heterogeneity pattern of the CMB is drastically different from that of the overlying D'' layer. Negative vertical travel time anomalies appear in the northern high-latitude region, and positive anomalies appear under Southeast Asia and Middle to South America. The lateral dimensions of these anomalies are of the order of 40¿. The anomalies can be interpreted as either a velocity perturbation in the boundary layer (¿~7% if the layer is 20 km thick) or an undulation of the CMB (¿~7 km). Various tests including the error and resolution estimations indicate that these three anomalies are the significant, resolvable features of the CMB. These anomalies are also corroborated by the result of the joint inversion of P and Pcp for both the 3-D mantle and the 2-D CMB. Assuming that the layer is laterally heterogeneous in iron content and deforms at the base in isostatic equilibrium with the outer core, the Pcp data are also inverted for the isostatic figure of the boundary layer. The velocity perturbation in this case is 5~6% if the layer is 20 km thick, and the CMB undulation is only ¿1~2 km. Regardless whether the CMB heterogeneity is due to velocity and/or topographic perturbations, it is dominant in the zonal component of degree 2, while the degree 2 pattern in the lower mantle, including the D'', is dominant in sectorial component.