Background In some patients with syncope health care is inappropriate and ineffective. In a recent observational investigation in community hospitals of the Lazio region of Italy (the OESIL study) 54.4% of patients admitted with syncope from the emergency room were discharged without a conclusive diagnosis. Aim of the Study A simplified two-step diagnostic algorithm was developed and prospectively implemented in nine community hospitals of the Lazio region of Italy in order to improve the diagnostic performance of clinicians, thereby reducing the number of undiagnosed patients. Study Population The study population included 195 consecutive patients (85 males and 110 females, mean age 62.5 years, range 13-95 years) presenting with a syncopal spell at the emergency room of one of the nine participating hospitals in a 2-month period. Results The systematic implementation of the proposed diagnostic algorithm resulted in a striking reduction of undiagnosed cases. The percentage of patients discharged without a conclusive diagnosis decreased from 54.4% to 17.5%. Neurally mediated syncope was diagnosed in 35.2% of cases, cardiac syncope in 20.9% and neurological syncope in 13.8%. Conclusions The use of specific, simplified diagnostic guidelines and algorithms results in an improvement of overall clinical performance. However, the development of such decision-making aids should carefully consider the local circumstances of daily clinical practice. (Eur Heart J 2000; 21: 935-940) (C) 2000 The European Society of Cardiology.