BACKGROUND: Little is known about the clinical presentation and course of novel H1N1 influenza in summer camps. OBJECTIVES: To describe the clinical course and evaluate the effect of influenza treatment in a summer camp population. STUDY DESIGN: Two large influenza outbreaks occurred in university-based residential camps between May 21 and August 2, 2009. Through active daily surveillance, medical evaluation at symptom onset, and data collection during isolation, we describe the clinical course of a large outbreak of novel H1N1 influenza. RESULTS: Influenza-like illness (ILI) was documented in 119 individuals. Influenza A was confirmed in 66 (79%) of 84 samples tested. Three early samples were identified as novel H1N1. ILI cases had an average age of 15.7 years and 52% were male. Sixty-three were treated with oseltamivir or zanamivir, which was initiated within 24h of diagnosis. Cough, myalgia and sore throat occurred in 69, 64 and 63% of cases, respectively. The highest temperature over the course of illness (T(max)) occurred within 48h after symptom onset in 87.5% of individuals. Average T(max) was 38.4 degrees C (range 36.1-40.2 degrees C). Among confirmed influenza cases, 69% defervesced by 72h and 95% defervesced by 96h. Defervescence at 72h was not different in the treated and untreated groups (p=0.12). CONCLUSIONS: Novel H1N1 generally has a mild, self-limited course in healthy adolescent campers. Defervescence occurred within 72h and was unaffected by treatment.