Investigations about porosity in petroleum reservoir rocks are discussed by Schmoker and Gautier. Pollastro discusses the uses of clay minerals as exploration tools that help to elucidate basin, source-rock, and reservoir history. The status of fission-track analysis, which is useful for determining the thermal and depositional history of deeply buried sedimentary rocks, is outlined by Naeser. The various ways workers have attempted to determine accurate ancient and present-day subsurface temperatures are summarized with numerous references by Barker. Clayton covers three topics: (1) the role of kinetic modeling in petroleum exploration, (2) biological markers as an indicator of depositional environment of source rocks and composition of crude oils, and (3) geochemistry of sulfur in source rocks and petroleum. Anders and Hite evaluate the current status of evaporite deposits as a source for crude oil.