The invention relates to a process for the preparation of aromatic polyester-carbonates wherein, in a first stage, aromatic oligo-esters or oligo-ester-carbonates having hydroxyl end groups are prepared from diaryl esters of aromatic dicarboxylic acids (or their starting materials) and diphenols and, optionally, a diaryl carbonate, by trans-esterification in the melt, and in a second stage these oligo-esters or oligo-ester-carbonates are condensed with phosgene by the phase boundary process to give the polyester-carbonate.