To determine the relative yields of Holter monitoring (HM), memory loop recording (MLR), and autotriggered MLR (AT-MLR), we retrospectively interrogated the very large database of Lifewatch (a Card Guard company and a commercial monitoring company) and compared the results obtained by each method. From among a total database of 100,000 patients, records of 1,800 patients from 2003 were randomly selected and examined, 600 from each of the 3 different monitoring groups. Each session of MLR and AT-MLR was applied for 30 days. For each patient we determined the symptomatic and asymptomatic events that were documented, including those that met predefined immediate physician notification criteria and the time to first notification event. The groups were identical in age and symptoms that necessitated monitoring; fewer women had HM. Information on the type of underlying structural heart disease, if present, and medications taken, if any, was not available to us in this database. The AT-MLR approach provided a higher yield of diagnostic events (e.g., 37, 108, and 216 total patients who had events; 37, 212, and 524 total events; and 6.2%, 17%, and 36% with a diagnostic yield for HM, MLR, and AT-MLR, respectively) and an earlier diagnosis. AT-MLR was also the most effective technique for capturing asymptomatic significant events, such as atrial fibrillation (52 with AT-MLR vs 1 for standard MLR). AT-MLR detected more than half as many asymptomatic episodes of atrial fibrillation (n = 52) as the total number of symptomatic episodes detected by patient activated recording (n = 94), thus confirming the common presence of asymptomatic atrial fibrillation. AT-MLR provided electrocardiographic documentation of tachyarrhythmias (n = 392) more often than MLR (n = 47) or HM (n = 44) and bradyarrhythmias/pauses/atrioventricular block (n = 38) more often than MLR (n = 13) or HM (n = 18). Thus, MLR and AT-MLR provide a diagnosis more often than does HM, thus confirming the benefit of prolonged monitoring. Further, the higher yield of AT-MLR versus MLR demonstrates the significantly enhanced benefit of autotriggered programmable recording.