Abstract: During polyoxyalkylation in the presence of certain double metal cyanide catalysts, a very high molecular weight hydrophobic fraction, i.e. a "tail", is produced during preparation of high secondary hydroxyl polyols which is believed to contribute to foam collapse in polyurethane foam formulations. The processing latitude of such foams may be improved by altering the hydrophile/lipophile balance of the high molecular weight tail by oxyalkylating with a mixture of ethylene oxide and higher alkylene oxide during the greatest portion of total oxyalkylation such that essentially pure higher alkylene oxide is present in a terminal portion of oxyalkylation not exceeding 15 weight percent of total polyol weight.