We present a case of two consecutive stress fractures in a female swimmer. The diagnosis of the present stress fracture of the ninth rib was based on clinical history and examination and on a new fracture line and callus formation seen in consequent conventional radiographs. Based on the clinical history and radiography, the patient had suffered another rib stress fracture in the fifth rib 15 months earlier. No external trauma had preceded either of the fractures, and no secondary cause of stress fracture was found. Her anatomical and biomechanical characteristics and training errors seem to have been responsible for the stress fractures. Sports physicians should be aware of rib stress fractures. With prompt diagnosis the rest period is short.