Abstract: In a pyrolytic furnace for the thermal cracking of hydrocarbons, cracking tubes are combined into uniformly arranged groups in the radiation zone of the pyrolytic furnace. The cracking tubes in the radiation zone consist of straight, vertically extending tube sections, manifold tube sections, and tube elbows. The cracking tubes of one group are joined, in the throughflow direction, via manifold tube sections and terminate in an outlet tube. The cracking tubes are arranged in the radiation zone in one plane, except for the juts of the tube elbows. The straight tube sections, subjected to a throughflow from the bottom toward the top and combined in the outlet tube, are located between the straight tube sections subjected to a throughflow from the top toward the bottom and leading into the tube elbows. The curvatures of respectively one-half of the tube elbows of one group extend in the same direction, the direction of curvature of the halves of the tube elbows being in opposition.