Fever is the most common chief complaint of children who refer to physicians. Its high incidence brings about the need for studying its cause, in order to determine the best approaches and managements and to avoid extra costs for the patients. This study is to determine the most common causes of fever in patients referring to our center, to evaluate the ability of paraclinical methods to help to diagnose the underlying cause, and to determine the necessary work up for each of the commonly seen causes. The study was done as a case series study on 457 acutely febrile children who referred to out patient department (OPD) of children medical center. The age range was from 3 month to 14 year. Fever was the chief complaint of 24.2% of patients referring to OPD. The predominant epidemiologic factors which increased the incidence of fever were female, working mothers and taking part in day care units. The underlying cause of fever was detected in 81.4% of cases only with clinical approach. The rest of the patients needed paraclinical work up for diagnosis of the cause of fever in them. The most common detected causes were: Upper respiratory tract viral infections (60%), Otittis media (9.8%), gastroentritis (8.5%), tonsiloapharyngitis (7.4%) and sinusitis (6.5%).According to our findings, the need for paraclinical work up to determine the underlying cause of fever in our patients has been much higher than similar studies done in other countries, this means that our physicians need more training in approach to febrile children and this goal can be achieved on continuous education courses.