Patients with unexplained syncope are often considered candidates for prolonged monitoring or empiric pacing when noninvasive and invasive investigations fail to provide a diagnosis. Identifying the outcome of patients undergoing prolonged monitoring that would ultimately benefit from empiric pacing may permit a cost-effective approach to resolution of syncope. Two hundred and six patients (age 57 +/- 18 years, 57% male) underwent prolonged monitoring with an implanted loop recorder for syncope of unknown origin. The median number of previous syncopal episodes was four (mean 29 +/- 133). Prior tilt testing was performed in 63% of patients, and electrophysiological testing in 46%. Symptoms recurred during follow-up in 142 patients (69%). Recurrence was associated with bradycardia leading to pacemaker implantation in 35 patients (17.0%), tachycardia in 12 (5.8%), sinus rhythm in 63 (30.6%), neurally mediated syncope based on rhythm and clinical assessment in 22 (11%), and failed activation in 10 (5%). Logistic regression analysis of baseline variables found that age was the only independent variable that predicted the need for pacing, associated with a 3% increase in risk per advancing year of age (odds ratio 1.027, P = 0.026). Despite this finding, no age group could be identified in which the likelihood of requiring pacing exceeded 30%. Logistic regression also found that patients with structural heart disease were less likely to experience recurrent symptoms during monitoring (49% vs 78%, P = 0.001) and that advancing age was associated with earlier recurrence of symptoms (P = 0.01). The etiology of recurrent syncope is diverse and cannot be predicted by baseline clinical variables. Empiric pacing appears to have little role in the management of this patient population.