- Respiratory tract infection (RTI) is a common diagnosis in the primary care setting. The aim of the study was to characterize the clinical course and laboratory manifestations of febrile RTI in Israeli adults presenting to primary care clinics. A prospective study over a 3-month winter period in 3 urban university primary care clinics of 122 consecutive adult patients seen by their family practitioners. All participants were interviewed and had chest radiographs, tests of oxygen saturation, and blood tests. Study group included 122 adults (mean age, 44.8 +/- 14.2 years; men, 38%). Fever lasted for a mean of 4.0 +/- 1.7 days, and the mean number of days off work/activities was 5.3 +/- 1.0. Pneumonia was clinically suspected in 33 patients (27%), but documented in 7 (6%). Antibiotics were given to 94 patients (77%). The group of treated patients had a lower mean oxygen saturation (P <.05) and a higher erythrocyte sedimentation rate (P <.05). Blood tests were found to be abnormal, although not clinically significant, in some patients, and all resolved spontaneously. RTIs are usually of short duration with a benign course where laboratory blood tests have no clinical implication. Radiographs may distinguish the 6% of patients having pneumonia from the 27% with suspected cases.