Background We evaluated an extended role for the physiotherapist in primary care in referring patients to plain X-ray. Methods This prospective cohort study was set in a single region in Sweden. It included 20 physiotherapists who were educated in a one-day training in performing referral to X-ray, along with 107 patients with musculoskeletal disorders who were referred to X-ray. We evaluated that referral quality, patient and physiotherapist satisfaction, and calculated health care and patient costs. Results All referrals fulfilled the basic requirements of quality, and 78% were classified as good, fulfilling all criteria. Both patients and physiotherapists were satisfied with the extended role for the physiotherapist that decreased waiting time to diagnosis and to adequate treatment. Costs were reduced for patients (by €53/patient) and health care (by €6286.2/107 patients). The cost to visit a physician was twice that of a physiotherapist visit. Conclusions An extended role for physiotherapists in primary care in referring patients to X-ray was effective and safe for patients and reduced costs for patients and for health care. Physiotherapists in primary care were able to refer patients to X-ray after one day of training, and the extended role freed up 45 minutes of physician time for each patient with a musculoskeletal disorder in need of an X-ray.