The following report reviews modern technology of radiant tubes with an emphasis on heat recovery and low-NOx combustion techniques, including flameless combustion. Performance of radiant tubes is of basic consequence in large strip line furnaces. The combustion patterns inside the tube, as well as connection of many tubes to the furnace, play a crucial role. The paper assesses the features related to this topic, from main design concepts to the materials available for radiant tubes, from energy saving measures to abatement of NOx emissions and flame/plant control. Significant applications to large industrial plants are reported, as well as on-going development of new products. Industrial practice and field feed-back point out that additional investment costs for an efficient and reliable radiant tube system can be recovered in a few years and provide better quality and operating conditions.