This invention relates to polymer polyols which comprise one or more base polyols, at least one preformed stabilizer, one or more ethylenically unsaturated monomers, and, in the presence of at least one free radical polymerization catalyst, and optionally, one or more polymer control agents. The base polyol of these polymer polyols comprises one or more amine initiated polyols. The present invention also relates to processes for preparing these polymer polyols, to foams prepared from these polymer polyols, and to processes for producing foams from these polymer polyols.