In a method for operating an internal combustion engine with exhaust gas purification system, a rich-burn mode of the internal combustion engine with a rich exhaust gas composition or a lean-burn mode of the internal combustion engine with a lean exhaust gas composition is set alternately, and the quantity of fuel which is introduced during a combustion cycle of the internal combustion engine is introduced by at least one preinjection, at least one main injection and at least one afterinjection.