Several hyperbranched polyesters With aliphatic and aromatic structural units and one hyperbranched polyamide were prepared by a AB(x) type polycondensation process in the melt or in highly concentrated solutions at temperatures above 150 degrees C. The structure of these polycondensates were determined and the polymer properties were analyzed. The hyperbranched polyesters have a degree of branching close to 50% and no indication of side reactions during polycondensation were found. The polyamide structures are more complex and analogous perfectly branched polyamides dendrimer segments up to generation four had to be usedas model compounds in order to study structural defects. All hyperbranched polycondensates are fully soluble in polar solvents and exhibit low solution viscosities.