Endemic dengue transmission has been documented in the Amazonian city of Iquitos, Peru, since the early 1990s. To better understand the epidemiology of dengue transmission in Iquitos, we established multiple active surveillance systems to detect symptomatic infections. Here we compare the efficacy of distinct community-based (door to door) and school absenteeism-based febrile surveillance strategies in detecting active cases of dengue. Febrile episodes were detected by both systems with equal rapidity after disease onset. However, during the period that both programs were running simultaneously in 2004, a higher number of febrile cases in general (4.52/100 versus 1.64/100 person-years) and dengue cases specifically (2.35/100 versus 1.29/100 person-years) were detected in school-aged children through the community-based surveillance program. Similar results were obtained by direct comparison of 435 participants concurrently enrolled in both programs (P < 0.005). We conclude that, in Iquitos, community-based door-to-door surveillance is a more efficient and sensitive design for detecting active dengue cases than programs based on school absenteeism. Copyright © 2009 by The American Society of Tropical Medicine and Hygiene.