Synchronous highs are “hills” on the sea floor present during sedimentation. Their origin may be diastrophic, depositional, erosional, or inherited through compaction or draping, or a combination of these. They tend to create conditions favorable to all three stages in the natural history of petroleum—origin, migration, accumulation—and are therefore thought to represent preferential habitats of oil and gas. This thesis is examined in the light of various modern observations and experimental data and exemplified through published descriptions and illustrations of numerous pools. Traps of this type may possess a variety of characteristic structural, topographic, sedimentary, and stratigraphic features which may be found in some cases through field, air-photo, or geophysical methods, but more commonly through careful studies of subsurface samples and logs.