The purpose of this study is to explore adherence by Dutch physiotherapists to the physiotherapists' guideline for non-specific low back pain. For this study data from the National Information Service for Allied Health Care were used. This is a registration network that continuously collects information about physiotherapy patients and their treatment episodes. Within this network, adherence to the low back pain guideline was assessed by three criteria based on the guideline. These criteria concerned the number of sessions, the treatment goals, and the interventions. Data from patients with 'non-specific low back pain' as the reason for referral and a completed treatment episode were selected (n = 1254); 90 therapists in 40 practices treated these patients. The criterion concerning the number of sessions applied only for patients with acute complaints and was met in 17% of these patients. In about half of the patients the criterion for the treatment goals as well as the criterion relating to the interventions was met. Treatment goals are aimed mainly at improving mobility functions and changing body position. In more than three-quarters of the treatment episodes manual interventions (massage or manual manipulation) and exercise therapy were used frequently. As considerable variation in guideline adherence was shown to exist among therapists, there is clearly room for improvement in the quality of the care.