Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering. Introduction Core analysis has come a long way from the days when reservoir productivity was determined by blowing through a piece of cable-tool-produced core. Our tools and methods for drilling and core analysis have changed, but our interests have not. The reservoir-rock properties that determine hydrocarbon production, the variation in these properties, and how these properties affectultimate recovery are still of primary concern. Properly engineered core analysis provides a direct measurement of these reservoir-rock properties and is an essential step in formation-evaluation, reservoir, and production engineering. Fundamental core-analysis measurements are unchanged, but advances provide the ability to test at reservoir conditions and to acquire simultaneous measurements of reservoir-dependent properties. Core analysis today uses X-ray computerized tomography (CT) to determine two- and three-dimensional (2D and3D, respectively) porosity distributions, while continuing to apply Boyle's law and Archimedes' principle to determine porosity. Mercury injection is used routinely to describe pore-throat distributions, but nuclear magnetic resonance(NMR) is becoming a popular method to delineate relationships between poreradii and permeability. This review addresses some recurrent concerns of core analysis as well as some new approaches and insights that are part of the physical reservoir model determined by core analysis. Refs. 1 through 6 provide more information on the subject. Coring and Field Operation Reservoir studies seeking to interpret and define both geological and engineering parameters dictate the core-analysis program. Core analyses mustintegrate with field and production data and eliminate reservoir uncertainties that cannot be addressed with log, well-test, or seismic data. These requirements define the coring objectives that, in turn, control coring fluid, tools, and core handling. In most cases, these objectives cannot be obtained with core retrieved in a single well. Coring is thus an integral part of the reservoir-life-cycle process, with cored wells selected to verify or provide maximum information for the current geological, engineering, or production model of the reservoir.