The aerodynamic characteristics of bridge sections can be determined by simple wind-tunnel tests. These characteristics can then be used to determine the lift force and overturning moment on any bridge section without large scale model tests. Also, the slope of the lift and torque curves obtained in these tests determine the aerodynamic stability or instability of the bridge section. Our problem was to determine the aerodynamic characteristics of typical bridge sections and attempt to find aerodynamically stable sections. The lift, torque and drag curves were obtained by holding the model stationary at different angles of attack in the wind-tunnel. The results obtained from these tests were confirmed by pressure distribution tests. In these tests the model was held stationary in the air stream, while pressure was measured by manometer readings at eleven points across the desk. Results of this investigation show that girder sections with deck at mid-height or flush are unstable except for low d/b ratios. Sections that yield both torsional and vertical stability are truss sections, an H-section with center slot and fins, and an H-section with fins. Other modifications of sections furnish curves which indicate neutrality. These sections can be used then sufficient damping is present. This investigation also shows that present wind-load specifications are inadequate and need to be revised. / Master of Science