Objective To retrospectively analyse the data of patients with suspected primary aldosteronism (PA) during the last five years.The receiver operating characteristic (ROC) curve was used to evaluate the value of aldosterone to renin ratio (ARR) in screening primary aldosteronism.Methods The clinical data of ARR in supine and upright positions were collected in 590 patients with suspected during January 2006 to August 2010.There were 357 patients diagnosed as primary aldosteronism and 233 patients as essential hypertension among these patients.100 patients with suspected primary aldosteronism took the upright and random ARR during September 2010 to April 2011 ; Among these patients,29 patients were diagnosed as primary aldosteronism and 71 as cases of essential hypertension.ROC curve was made to retrospectively define the method and the cut-off value of the supine,upright or random ARR.Results The area under the curve(AUC) of the supine ARR in the 590 patients who took the supine and upright ARR during January 2006 to August 2010 was 0.838 (0.805-0.867 ) and the AUC of the upright ARR was 0.873 (0.843-0.899 ).There was significant difference between these two AUC readings (P＜0.01 ).The AUC in the upright ARR of the 100 patients who took the upright and random ARR during Septeuder 2010 to April 2011 was 0.962 (0.928 -0.995 ) and the AUC of the random ARR was 0.944 (0.893-0.994 ).There was no significant difference between these two AUC readings (P＞0.05).The upright ARR cutoff value with 400 ( pg · ml-1 )/( ng· ml-1 · h 1 ) yielded a sensitivity of 91.9％ and a specificity of 64.2％ to diagnosis of PA.Conclusion Upright ARR value was more suitable in the screening test than supine ARR value.Random ARR showed similar effect as the upright ARR.In our research,under strict control of the drug,position and detection time,ARR value with 400 ( pg · ml-1 )/( ng· ml-1 · h-1 ) can be the cutoff point in screening the suspcctcd PA patients.