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An electrophotographic toner composition suitable for heat-fixation and showing good storage characteristics is constituted by polymer components, a colorant and a metal-containing organic compound. The toner composition shows a melt index (at 125.degree. C., 10 kg-load) of 5-25 g/10 min., and the polymer components are characterized by (a) containing substantially no THF (tetrahydrofuran)-insoluble content, (b) including a THF-soluble content thereof providing a GPC (gel permeation chromatography) chromatogram showing i) a main peak in a molecular weight region of 2.times.10.sup.3 -3.times.10.sup.4, and a sub-peak or shoulder in a molecular weight region of at least 10.sup.5, and ii) an areal percentage of 3-10% in a molecular weight region of at least 10.sup.6, and (c) including a polymer component (H) in a molecular weight region of at least 10.sup.5 obtained by polymerization using a polyfunctional polymerization initiator and a monofunctional polymerization initiator.

A magnetic toner for developing an electrostatic image has magnetic toner particles containing at least a binder resin and magnetic iron oxide particles. The magnetic iron oxide particles have been surface-treated with an aliphatic alcohol having carbon atoms of from 12 to 300 on the average. The magnetic toner has a weight average particle diameter of 13.5 .mu.m or smaller, and contains magnetic toner particles with particle diameters of 3.17 .mu.m or smaller in an amount not less than 1% by number as number-based percentage determined from number distribution.

A toner for developing electrostatic images includes a binder resin, a specific long-chain alkyl compound and a specific azo iron complex. The long-chain alkyl compound contains a terminal --OH or --COOH group and from about 35 to 150 (--CH.sub.2 --) groups. The azo iron complex has a cation including 75-98 mol. % of ammonium ion and another ion which is hydrogen, sodium, potassium or mixtures thereof.

A magnetic developer for developing electrostatic images is constituted by magnetic toner particles, each containing a binder resin having a melt viscosity of at most 5.0.times.10.sup.6 poise at 150.degree. C. and a magnetic material. The magnetic material is blended with a proportion (C) [wt. %] of inorganic fine particles based on the magnetic material to carry 0.2-5 wt. % of the inorganic fine particles secured to the magnetic material surface. The magnetic material has a specific surface area (A) [m.sup.2 /g] before securing of the inorganic fine particles and is provided with an increase in surface area (B) [m.sup.2 /g] by the securing of the inorganic fine particles; wherein the parameters A, B and C satisfy the following formulae (1) and (2): As a result, the magnetic developer is provided with an improved low-temperature fixability without causing problems accompanying the use of a low-temperature softening binder resin, such as deterioration of anti-offset characteristic, storage characteristic, developing characteristic.