An investigation has been made of the relationships governing the thermal decomposition of kerosine used as a diluent in the pyrolytic synthesis of estrone. it has been established that, under estrone synthesis conditions, kerosine is subjected to thermal decomposition, leading to the formation of unsaturated hydrocarbons, and also resins and coke, which shortens the running time of the unit. On the basis of the results obtained and an analysis of published data, it is recommended that estrone synthesis be carried out under conditions of short contact times, with the use of a lighter hydrocarbon with a high H/C ratio as the diluent. This promotes an increase in the actual concentration of hydrogen atoms in the reaction mixture and a reduction in the coke formation rate.