A process is herein disclosed for decreasing olefin and diolefin unsaturation of pyrolysis naphtha (dripolene) without concomitant production of gum, heavy polymers, and/or coke; which process comprises treating pyrolysis naphtha with water at a temperature in the range of 500.degree.-700.degree.F at an elevated pressure in the range of 700-4000 psig for a residence time of from about 12 minutes to about 10 hours under conditions such that a portion of the treating water remains in the liquid phase. Treated naphtha product from said treating step, substantially reduced in olefinic and diolefinic unsaturation and essentially free of gum, heavy polymers and coke, may be hydrotreated with molecular hydrogen in the presence of a hydrogenation catalyst for further reduction of olefinic and diolefinic unsaturation and removal of sulfur compounds.