A method is disclosed for treating the effluent from a hydrocarbon pyrolysis unit without employing a primary fractionator. The method comprises cooling the gaseous effluent, e.g., by direct quench and/or at least one primary heat exchanger, thereby 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 resulting mixed gaseous and liquid effluent is passed through a quench oil knock-out drum, to separate quench oil from the gaseous effluent which is then cooled to condense a liquid effluent comprising pyrolysis gasoline and water condensed from steam, which fractions are separated in a distillate drum. The cooled gaseous effluent is directed to a recovery train, to recover light olefins. The pyrolysis gasoline-containing fraction passes to a tailing tower which provides an overhead stream rich in pyrolysis gasoline and a bottoms stream rich in gas oil.