There is a clear need in most developed countries to increase the level of physical activity to achieve a recognized public health gain. It has been suggested that walking is 'the nearest activity to perfect exercise' (Morris and Hardman, 1997: Sports Medicine, 23, 306-332). Walking is one mode of activity that most people can do without skills, equipment, facilities or extra expense and walking has less bias in terms of age, sex and social class than more structured activities. The aim of this study was to determine, using the transtheoretical model of behaviour change (Marcus and Simkin, 1994: Medicine and Science in Sports and Exercise, 26, 1400-1404) as a theoretical framework, how people increased their walking behaviour. It is part of a larger study investigating the physiological and psychological effects of self-paced walking.