Propylene oxide was anionically polymerised in bulk at 80°C under a range of initial conditions, from zero hydroxyl content to a mole ratio of hydroxyl to potassium catalyst of 10. The double bond content of the polymers was measured by 1H NMR spectroscopy over a wide range of conversions, and values of the transfer constant were determined. The results were fitted to a reaction mechanism involving suppression of the transfer reaction by hydrogen bonding of hydroxyl groups to active ion pairs. The head-to-head content of the polymers was measured by 13C NMR spectroscopy. The overall proportion (approximately 4%) of ‘head-to-head’ reactions relative to head-to-tail addition was not greatly affected by suppression of the transfer reaction, since an increase in the number of head-to-head additions compensated the decrease in proton abstraction from methyl groups via the transfer reaction.