The Authors analyse the clinical and radiographical results of 14 patients (16 feet) affected by hallux valgus (HV) in flexible abnormal pronation syndrome. Patients were treated by distal osteotomy of the first metatarsal bone and sub-talar arthroereisis in one stage. This treatment was chosen because HV is often associated with abnormal foot pronation. Patients were young and the sub-talar joints had good mobility. The protocol forecasts: X-ray study of the feet and post-surgery planning, day surgery admission, minimally invasive surgery and 5 weeks of immobilisation in a below-knee cast.