Data from 47 reversed seismic refraction profiles in the northeastern Gulf of Mexico are presented in the form of four east-west and two north-south cross sections. Where possible, correlations are drawn between velocity layers encountered offshore and well data from various oil wells drilled on the Florida mainland. The Peninsular arch of Florida is shown to exhibit a lobe-like extension on its western limb, affecting the attitude of the pre-Cretaceous basement rocks. Under the eastern part of the extreme northeastern Gulf of Mexico, interpretation of the seismic records is complicated by the presence of strata with lower seismic velocities than the material above. Evidence is presented that these strata lie somewhere near the top of the Upper Cretaceous. The subsurface eology beneath the continental shelf in this area generally parallels that of northern Florida, exhibiting the lateral dual facies relationship of clastic sediments in the west grading to carbonates in the east. Evidence points to the possible existence of scattered reefal deposits in the Upper Cretaceous along the extrapolated axis of the Suwannee strait.