This invention relates to nitrile-free azo initiators for the preparation of polymer polyols and to the polymer polyols prepared therefrom. These novel polymer polyols comprise a base polyol, a preformed stabilizer and at least one ethylenically unsaturated monomer, in the presence of at least one free-radical polymerization initiator comprising as azo compound that is free of nitrile groups, and optionally, a polymer control agent. The process of preparing these polymer polyols is a continuous process comprising free-radically polymerizing a base polyol, a preformed stabilizer, and at least one ethylenically unsaturated monomer, in the presence of at least one free-radical polymerization initiator comprising as azo compound that is free of nitrile groups, and optionally, a polymer control agent.