Atom probe tomography (APT) is a powerful materials characterization technique capable of ppm chemical resolution and near atomic scale spatial resolution. However, owing to a number of factors, the technique has not been widely applied to insulating materials and even less to complex oxides. In this study, we outline the methodology necessary to obtain high-quality results on a technologically relevant complex oxide Pb(Zr,Ti)O-3 (or PZT) using laser-assisted APT on both bulk and thin film specimens. We show how, with optimized and well-controlled conditions, APT complements conventional techniques such as STEM-EDS. The correlative information can be used to obtain the nanoscale 3-D chemical information and investigate the nanoscale distribution of cations. Using nearest-neighbor cluster analysis routines, 5-10nm segregation of B-site cations was detected in bulk sintered PZT 53/47 from chemically prepared powders. No statistically significant segregation of B-site cations was observed in thin film specimens. This work opens new avenues toward understanding the process-structure properties in complex materials at length scales heretofore unachievable.