A method is described of dry distillation of bituminous materials by leading warm combustible gases, mixed or not mixed with steam, through the distillation chamber in direct contact with the materials, during which process the distillation chamber may be heated by other means. It is characterized by the mixture of distillation products (formed by the vapors produced by heating the raw materials) and the gas (circulating gas) used for heating in the process, being led through coolers or similar contrivances, in order to separate through condensation the greater part of the content of the products or materials condensable at ordinary temperatures, and also to recover as much as possible of the highly volatile oils in the gas. Thereafter the gas is split, one part is, without further cleaning, and led through the distillation chamber, after this gas has been reheated in suitable apparatus. The other part (surplus gas), which in volume corresponds approximately to the new-formed distillation gases, is treated according to known methods for the extraction of the remaining products of the distillation, such as volatile oils, ammonia, methyl alcohol, sulfuretted hydrogen, and others. The patent contains three other claims.