Since implantable loop recorders (ILRs) were first developed, extensive clinical investigation and important improvements have made them an integral part of modern cardiology practice. The ILR has traditionally been used in the work-up of recurrent, unexplained syncope, but recent studies have explored its usefulness in post–myocardial infarction risk stratification, in the work-up of cryptogenic stroke, and in the postprocedure follow-up of patients undergoing atrial flutter and atrial fibrillation ablation. This article reviews the design, functionality, and pitfalls of modern ILRs, along with typical recordings obtained from patients with unexplained syncope.