A structural reconnaissance study of the San Diego mainland shelf, off southern California, was conducted using ship-towed Edo 3.5 KHz high-resolution and "Uniboom" deep-penetration acoustic profiles. The focus of the study was on mapping the structural aspects of the shelf, and secondarily, on determining what effects, if any, these features had on the distribution pattern of the unconsolidated sea floor sediments. The shelf region is a broad, flat, submerged portion of the mainland extending a maximum of 18 kilometers in width and to a depth of about 100 meters. Faulting is common and is found to the north of La Jolla Bay with the offshore extension of the Rose Canyon fault, west of Mission Bay offshore as a fault bound basin, and to the south with numerous north-south-trending faults in the San Diego bight region. Upper Cretaceous rocks underlie the shelf and are folded in gentle upright folds that trend northwesterly. The folds are suggested to be as young as late Pleistocene from onshore data. Structural features influence local accumulation and thinning of unconsolidated sediment as a result of relief inversion, fault scarps, and sea floor warping.