A feasibility study was performed to determine if infrared thermography could be used to detect perturbations in the arc welding process that result in defects. Data were gathered using an infrared camera with a resolution of 0.2°C, which was trained on the molten metal pool during welding. Several defects were then intentionally induced, and the resulting thermal images were preserved on film. These images revealed that different types of weld defects induce different characteristic changes in the thermal image by detectably altering the temperature field around the weld. These perturbations in the temperature field can be used to identify and locate defects such as arc misalignment, plate gap, puddle impurities, etc. Macrostructural examinations permitted investigations into the relationships between weld puddle penetration depth and the temperature field. Using computer-aided processing of these thermal images, we expect that the welding process can be controlled to a higher degree than is presently possible.