Acute low back pain is a commonly occurring symptom that can impact considerably upon a person's life. It is poorly defined, difficult to classify and challenging to measure. However, due to the high prevalence rates of the symptom, cited in the epidemiological literature, and the costs incurred by individuals, health services and society in general, it is vital that clients are encouraged to take more responsibility for their health. This thesis is concerned with perceptions of control in people with acute low back pain. It is about how they respond to this symptom and the way it impacts upon their lives. The underpinning literature is drawn from both medical and social science research, as the work crosses faculty boundaries. Problems are addressed from a physiotherapeutic and social science perspective, as links are formed between the different disciplines. From this literature, a significant theoretical development was the creation of a framework, which enabled the systematic review of existing outcome measures. A number of instruments, relevant to clients with acute low back pain, were reviewed using this framework, for the dimensions of control, function, pain and anxiety. The findings were used to inform the selection of outcome measures in this research. Four studies were then undertaken, all linked to studying clients with acute low back pain. The first study was a survey of general practitioners in Southampton and the New Forest, which identified their strategies for managing clients with acute low back pain. The second study focused on clients' experiences and was a randomized controlled trial, which tested the effectiveness of an information leaflet, designed to encourage clients to take more responsibility for their own health. The third study primarily focused on clients' perceptions of control over time, addressing the question of how these perceptions change during a one-year period. Finally, since recruitment of clients by their doctors was problematic throughout this research, a follow-up survey was undertaken with these health professionals to establish the reasons for this. The results of these studies are used to discuss the importance of clients' perceptions of control and the implications for clinical practice.