A toner for developing electrostatic images is formed from toner particles containing at least a binder resin, a colorant, and a wax. The binder resin comprises a vinyl polymer component and a polyester component. The binder resin contains 40-99 wt. % of a component A, 0-20 wt. % of a component B, and 0-60 wt. % of a component C, the components B and C providing totally 1-60 wt. % of the binder resin. The component A comprises low- and medium-molecular weight components having molecular weights of below 10.sup.6, and the component B comprises high-molecular weight components having molecular weights of at least 106, respectively, based on a chromatogram obtained by gel permeation chromatography of a tetrahydrofuran (THF)-soluble component of the binder resin, and the component C is a THF-insoluble component of the binder resin. The GPC chromatogram of the THF-soluble component of the binder resin exhibits a main peak in a molecular weight region of 3.times.10.sup.3 -5.times.10.sup.4. The toner particles have a shape factor SF-1 of 100-160 and a shape factor SF-2 of 100-140.