An improved process for steam cracking a crude oil feed to produce products useful as chemical raw materials or fuels characterized by the steps wherein the crude oil feed is first passed through the convection section of a steam cracking furnace to vaporize the materials in the feed boiling below about 450.degree. F., i.e., a naphtha fraction. The vaporized portion of the crude oil feed is then separated from the liquid portion of the feed by passing the liquid and vapor fractions into a separation zone, i.e., a flash drum separator wherein the vaporized portion of the feed passes overhead and is then fed, with steam, into the steam cracking furnace and subjected to short residence time, high-temperature cracking conditions. The liquid portion of the feed i.e., nonvaporized portion which settles to the bottom of the flash drum separator is withdrawn therefrom and passed through the convection section of a second steam cracking furnace and thereafter into a second separation zone. By introducing steam into the second zone, i.e., flash drum separator, materials boiling above about 450.degree. F. and below about 1,100.degree. F., i.e., the gas oil fraction of the crude, pass overhead from the separator and are then introduced into a second steam cracking furnace, without the need to further add substantial amounts of diluent steam, to be cracked under optimum gas oil fraction cracking conditions.