The methods available for the preparation of star-branched polymers are described. After presentation of theoretical predictions of the effect of this type of branching on the properties of polymers, available experimental data are compared and critically discussed. Thermodynamic and visco-elastic properties at infinite dilution are first presented followed by visco-elastic properties in concentrated solution and the melt. Finally the effect of star-branching on T//g of low molecular weight polymers is described.