Aims - An observational cohort study in patients undergoing treatment at a single cancer centre to evaluate the usefulness of providing written information on exercise and fatigue to patients at the start of their treatment, to assess whether patients exercised during treatment and their level of fatigue before and after treatment. Materials and methods - Participants were 205 patients of mean age 63.4 years (115 men and 90 women), starting a course of radical radiotherapy, postoperative radiotherapy and palliative radiotherapy or chemotherapy between October 2004 and June 2005 for genitourinary, gynaecological or breast cancer. A patient-held folder was provided, containing written information on cancer or treatment-related fatigue and the use of exercise to manage this, together with flyers for workshops on fatigue management held at local palliative care centres. Study evaluation questionnaires were used for patients to rate the information's usefulness and provide information regarding fatigue. Fatigue level was documented using Brief Fatigue Inventory score sheets. The main research variables were patient rating of the usefulness of the written information provided, whether patients reported being able to exercise during their cancer treatment and self-completed fatigue scores. Results - The information provided was rated as helpful or very helpful by 70?78% of patients. Overall, 144/163 patients (88.3 reported exercising during treatment (70.2% of all patients in the fatigue initiative). Patients receiving radical or postoperative radiotherapy as compared with chemotherapy, and those using the information supplied were more likely to exercise during treatment. There was a significant overall increase in mean fatigue from the start to the end of cancer treatment (P 60; 0.001). Patients who did not exercise, younger patients, those with breast cancer and those receiving chemotherapy (compared with radical or postoperative radiotherapy) all had higher fatigue scores. Conclusions - Provision of written information on exercise to manage fatigue was rated as helpful by most patients receiving cancer therapies; patients who were able to exercise during treatment had lower fatigue levels.