Objectives: To identify the clinical characteristics of outpatients with flu-like illnesses stratified by influenza A H1N1 status. Methods: The study was conducted at the H1N1 staff clinic of Sultan Qaboos University Hospital in Muscat, Oman. The population consisted of university students and university/hospital staff and their family members. All adult patients who presented to the H1N1 clinic with an influenza-like illness over a 4-month period (from August until the end of November 2009) were included. Real-time reverse transcriptase (rRT) PCR was used for the diagnosis of H1N1 influenza. Demographic data, clinical signs and symptoms, history of exposure to H1N1, history of recent travel, and co-morbid conditions were documented. Analyses were conducted using univariate and multivariate statistical techniques. Results: Out of the 2318 patients identified, 27% (n= 616) were positive for H1N1 influenza. The mean temperature in the H1N1-positive group was significantly higher than in the negative group (38.3 °C vs. 37.2 °C; p< 0.001). Proportions of patients who reported cough, sore throat, headache, myalgia, gastrointestinal symptoms, exposure to a confirmed case of H1N1, and a history of travel were significantly higher in the H1N1-positive group as compared to the swab-negative group. However, the multivariable logistic model identified only the following significant predictor variables of H1N1 infection: younger age, fever (≥37.8 °C), sore throat, myalgia, diarrhea, and exposure to a confirmed H1N1 case within the last 7 days. Conclusions: This study provides useful data on the clinical characteristics of H1N1 influenza in a large outpatient population from the Middle East. Patients who tested positive for H1N1 were more likely to have fever, sore throat, diarrhea, and myalgia compared to those with other influenza-like illnesses.