A method is disclosed for treating the effluent from a hydrocarbon pyrolysis unit without employing a primary fractionator. The method comprises passing the gaseous effluent to at least one primary heat exchanger, thereby cooling the gaseous effluent and generating high pressure steam, and then cooling the gaseous effluent to a temperature at which tar, formed by reactions among constituents of the effluent, condenses. The gaseous effluent and the condensed tar are fed to at least one knock-out drum, whereby the tar is separated from the gaseous effluent. The gaseous effluent is then further cooled to condense a pyrolysis gasoline fraction from the effluent and to reduce the temperature of the effluent to a point at which it can be compressed efficiently. The condensed pyrolysis gasoline fraction is separated from the effluent and then distilled so as to reduce its final boiling point.