A reaction system comprising an organic polyisocyanate and an isocyanate reactive component for preparation of a viscoelastic polyurethane foam is provided. The isocyanate reactive component comprises (i) from 10 to 50% by weight of one or more low equivalent weight propylene oxide rich (PO-rich) polyols having a combined number average equivalent weight from 200 to 500, (ii) from 45 to 95% by weight of one or more ethylene oxide (EO-rich) polyols having a combined number average equivalent weight from 200 to 800 and an ethylene oxide content from 40% to 65% by weight of the total mass of the EO-rich polyol and at least one of (iii) from 10 to 30% by weight of one or more high equivalent weight PO-rich polyols having a number average equivalent weight from 800 to 2,000 or (iv) from 10 to 40% by weight of one or more propylene oxide co-polymer polyols containing styrene-acrylonitrile.