Hyperbranched alkyd resins (HBRA) were synthesized by modification of hydroxylated hyperbranched polyester (HBP1-4) with tall oil fatty acids (TOFA). The core is a hydroxylated hyperbranched polyester of fourth generation with OH groups in the periphery (18), which is endcapped with tall oil fatty acids. The occurrence of these reactions, HBP1-4 and TOFA, was determined by making use of acid value, nuclear magnetic resonance, and hydroxyl values. The effects of TOFA and HBP1-4 on properties of the HBRA resins were investigated by vapor pressure osmometry, differential scanning calorimetry, thermogravimetric analysis, friction resistance, and hardness. The resins with higher modification percentage (HBRA4) presented the best thermal and hydrolytic stability, but lower friction resistance and hardness. All HBRA resins presented amorphous characteristics, OH groups, and double bonds in the periphery. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 3151-3158, 2011