A process for producing a flexible polyurethane foam, comprising reacting at least one diisocyanate or polyisocyanate component, with an isocyanate-reactive component comprising at least polyether polyol having a functionality of from 2 to 6 and a molecular weight of from 700 to 14,000; at least one polymer polyol having a solids content of greater than 20% by weight, a total ethylene oxide content of up to 25% by weight, having a viscosity at 25°C of less than 15,000 mPa.s, and comprising a reaction product of at least one base polyol containing active hydrogen atoms having a molecular weight of less than 14,000 and a total ethylene oxide content up to 40% by weight, said base polyol being formed in the presence of a DMC catalyst, at least one unsaturated monomer, and, a preformed stabilizer, in the presence of; at least one free radical initiator that comprises a peroxide, and optionally a chain transfer agent; and one or more chain extenders and/or crosslinking agents having a functionality of from 2 to 3, and a molecular weight of from 300 or less; in the presence of one or more blowing agents, and, optionally, one or more additives and/or auxiliary agents; at an Isocyanate Index of from 90 to 120. at least one diisocyanate or polyisocyanate component, with an isocyanate-reactive component comprising at least polyether polyol having a functionality of from 2 to 6 and a molecular weight of from 700 to 14,000; at least one polymer polyol having a solids content of greater than 20% by weight, a total ethylene oxide content of up to 25% by weight, having a viscosity at 25°C of less than 15,000 mPa.s, and comprising a reaction product of at least one base polyol containing active hydrogen atoms having a molecular weight of less than 14,000 and a total ethylene oxide content up to 40% by weight, said base polyol being formed in the presence of a DMC catalyst, at least one unsaturated monomer, and, a preformed stabilizer, in the presence of; at least one free radical initiator that comprises a peroxide, and optionally a chain transfer agent; and one or more chain extenders and/or crosslinking agents having a functionality of from 2 to 3, and a molecular weight of from 300 or less; in the presence of at least polyether polyol having a functionality of from 2 to 6 and a molecular weight of from 700 to 14,000; at least one polymer polyol having a solids content of greater than 20% by weight, a total ethylene oxide content of up to 25% by weight, having a viscosity at 25°C of less than 15,000 mPa.s, and comprising a reaction product of at least one base polyol containing active hydrogen atoms having a molecular weight of less than 14,000 and a total ethylene oxide content up to 40% by weight, said base polyol being formed in the presence of a DMC catalyst, at least one unsaturated monomer, and, a preformed stabilizer, in the presence of; at least one free radical initiator that comprises a peroxide, and optionally a chain transfer agent; and at least one base polyol containing active hydrogen atoms having a molecular weight of less than 14,000 and a total ethylene oxide content up to 40% by weight, said base polyol being formed in the presence of a DMC catalyst, at least one unsaturated monomer, and, a preformed stabilizer, in the presence of; at least one free radical initiator that comprises a peroxide, and optionally a chain transfer agent; one or more chain extenders and/or crosslinking agents having a functionality of from 2 to 3, and a molecular weight of from 300 or less; one or more blowing agents, and, optionally, one or more additives and/or auxiliary agents; at an Isocyanate Index of from 90 to 120.