A seismic refraction experiment to determine crustal structure of the northern margin of the Gulf of Mexico was made along long. 94°W during the fall of 1966. The quality of the records was generally good, although for some shots no signals were recorded because of anomalously high attenuation in the vicinity of the shot point. This study shows the crust beneath Texas to be approximately 49 km thick, that beneath the shelf to be about 33 km, and that beneath the subshelf to be about 27 km. The low-velocity part of the sediments (1.9-3.3 km/sec) is approximately 10 km thick on the shelf, and thins on the north and probably also on the south. Inasmuch as the crust beneath the shelf is much thinner than that beneath land, we suggest that the sediments of the Gulf Coast ere not deposited on a normal continental crust and that most of them may have been deposited in water of moderate depth.