Steam furnaces encountered in chemical and power generation plants often experience a maldistribution of steam temperature at furnace tube outlets despite attempts to ensure good flow distribution in these tubes from the inlet feed header. An investigation of an existing tube bank configuration was carried out utilizing field measurements, a CFD analysis of the thermal/flow field, flow experiments with a 1:7 scale laboratory model using air as the working fluid, and a 1-D analysis of the temperature/flow distribution. The results indicate that although the inlet header does not actually run through the furnace, heat transfer by conduction from the tube walls to the inlet header wall causes preheating of the incoming steam, resulting in a substantial increase in steam temperature towards the end of the header. This steam temperature maldistribution at the inlet to the tubes persists along the tubes and manifests itself as a similar maldistribution in the tube skin wall temperatures. The latter has an impact on the system integrity if the skin wall temperature exceeds the metallurgical limit of the tube material used.