A small boat-based seismic reflection survey was conducted on the Mississippi River across the New Madrid seismic zone. One second (1400--2000 m depths) of 12 fold, high resolution data were recorded along approximately 240 km of the river. Because of differences in the quality of the data along some parts of the river and because of geologic complexities, a mixture of marine-based and land-based data-processing methods were used to get the best profiles. The data suggest reflections from Paleozoic, Late Mesozoic and Cenozoic strata and some faults and slight local flexures. A probable extension of the Cottonwood Grove fault, a feature discovered with land-based seismic reflection profilling, was identified about 5 km south-east of Caruthersville, Missouri. This fault is subparallel with the northeast trend of epicenters in the New Madrid seismic zone. In addition to providing subsurface data along the river where land-based reflection surveying cannot be done, the river survey provided data on a wealth of shallow geologic features at minimal cost.