Aqueous alkyd resins

An aqueous alkyd resin obtained by the neutralization of a polycondensation resin with a base, the polycondensation resin being prepared by reacting a reaction mixture obtained by the transesterification or esterification of (a) a natural fat and oil or a fatty acid with a polyhydric alcohol with an adduct of (b) a liquid polybutadiene having a number average molecular weight of 150 to 900, a viscosity of 2 to 80 cps;. at 30.degree. C and at least 50% of the cis-1,4 structure with an .alpha.,.beta.-unsaturated dicarboxylic acid or the anhydride thereof, and/or the half-ester of said adduct, and (c) an aromatic polycarboxylic acid or the anhydride thereof, the proportion of the component (b) to the component (a) being in the range of 0.1 to 0.7 by weight, as calculated by (b)/(a) + (b), the polycondensation resin having free carboxyl groups in the amount corresponding to an acid value of 30 to 70 and containing 5 to 50% by weight of the component (b), wherein the total amount of the components (a) and (b) is in the range of 30 to 85% by weight on the basis of the whole resin.