Walking groups are increasingly being set up to increase physical activity in sedentary population groups, but little is known about whether they are effective at doing so and how they work. The present thesis aims to build an evidence base of whether walking groups are effective at promoting public health and what factors account for their effectiveness. Methods: Four studies were conducted to address the overall aim. Study One: a systematic literature review with meta-analysis investigated whether interventions to promote walking in groups are effective at promoting physical activity. Study 2: a multi-perspective thematic analysis of interviews with walkers, walk leaders and walk co-ordinators, includingfollow up interviews with walkers, explored whether the needs and expectations of people who participated in walking groups were satisfied. The sample was gained from walking schemes run by Coventry City Council. Study Three: awalk-along interview study with walk leaders explored what and how environmental factors are seen to affect walking behaviours in groups. Study Four: a prospective cohort survey explored what theoretical constructspredict maintenance of attendance at walking groups in the Midlands. Results: Study One:interventions to promote walking in groups were found to be effective at promoting physical activity within efficacy studies targeting adults (d=0.42). Study Two: walkers reported that they joined walking groups to gain social and health benefits. Three months later the same walkers reported that they continued attending walking groups when their initial needs were satisfied by the other people in the group. Walk leaders and walk coordinators often acknowledged the same reasons but expressed lack of confidence to effectively address them. Study Three: walk leaders describedenvironmental factors that were important facilitators for behaviours within walking places. Lap walking places were reported to facilitate physical activity, park walking places were reported to facilitate social interactions and city centre walking places were reported to facilitate time efficient behaviours. Study Four: recovery self-efficacy and satisfaction with outcome expectancies and overall experiences within the groups were found to predict maintenance of attendance at walking groups. ix Conclusions:The results of this thesis suggest that walking groups increase physical activity. Furthermore, successful walking groups should include theory based techniques to promote behaviour change and social integration within participants. The outcomes of this thesiscan be used as an evidence base for developing, implementing and evaluating effective walking groups within the community.