Abstract: Cracking of crude oil or crude oil residues is accomplished in an adiabatic reactor which follows a partial combustion zone with the injection of superheated or shift steam into the combustion gases.Advantages are that the carbon monoxide produced by partial combustion is converted to carbon dioxide which is easily removed, there is no need to supply a separate source of fuel or hydrogen, and coke formation is substantially eliminated. The cracked oil produced in the process can be used as a quench oil and/or fuel to feed the partial combustion zone. The yields of olefins and aromatics is increased over processes using superheated steam cracking.