Upper respiratory tract infections caused by adenoviruses present long lasting fever for five days and elevated acute phase reactant levels. They are generally misdiagnosed as bacterial infections and are mistreated with antibiotics. The diagnosis of adenovirus infections mainly depends on direct antigen tests, virus isolation and detection of viral DNA using polymerase chain reaction (PCR). The aim of this study was to evaluate the clinical and laboratory findings of the children diagnosed as adenoviral respiratory tract infection by multiplex PCR (mPCR). A total of 27 children (18 male, 9 female; age range: 17 years, mean age: 4.4 years) whose nasopharyngeal swab samples were found positive for adenovirus DNA with a commercial mPCR method (Seeplex (R) RV15 ACE Detection Kit, Seegene Inc, Korea) were included in the study. The throat cultures of the patients revealed no bacterial pathogens and EBV VCA-IgM antibodies were negative. The clinical and laboratory data of the children with long lasting high fever diagnosed as adenovirus infection were evaluated retrospectively in terms of their complaints on admission, symptoms detected in physical examination, laboratory findings and therapy protocols. The patients were categorized according to hospitalization period (<3 days or >= 3 days) and also according to the symptoms compatible with upper or lower respiratory tract infections. The quantity of clinical symptoms <= 2 or >2) and the presence of upper or lower respiratory tract findings were evaluated if there were a difference by means of hospitalization rate and period. The most common complaint of the patients with adenoviral respiratory diseases was fever (27/27; 100%), and the most common admittance season was april-may-june period (20/27; 74%). The mean temperature was 38.4 degrees C (range: 38-39.8 degrees C) and the fever continued for 1-5 days after hospitalization. The most common physical examination finding was tonsillary hyperemia and hypertrophy (63%), followed by lower respiratory tract disease symptoms (37%), otitis media (14.8%), conjunctivitis (7.4%), and rash (3.7%). Laboratory tests could be performed for 24 cases and 95.8% of them yielded high CRP level, 87.5% high sedimentation rate, 62.5% neutrophilia, 33.4% leukocytosis and 20.8% lymphocytosis. It was noticed that 85.2% (23/27) of the patients were under antibiotic treatment on admission. Twenty-three patients (85.2%) were hospitalized, and the duration of hospitalization was between 1-8 (mean: 3.78) days. When the hospitalization rate was evaluated in terms of different measures, it was found that the rate was 81.8% (18/22) in patients with <= 2 symptoms, 100% in patients with > 2 symptoms (5/5); 100% (10/10) in patients with lower respiratory tract disease symptoms; 100% (15/15) in patients with neutrophilia, 88.2% (15/17) in patients with CRP levels of >= 2.8 - <100 mg/L, and 100% (6/6) in patients with CRP levels of >= 100 mg/L. Neutrophilia and high CRP levels were found to be the main factors related to the hospitalization rate (p<0.05). In conclusion, adenoviral etiology should be determined by a rapid and sensitive laboratory method such as mPCR, in cases with tonsillopharyngitis who exhibit leukocytosis, neutrophilia and high CRP levels and no bacterial pathogens in throat culture, in order to prevent unnecessary antibiotic use and hospitalization.