Acute respiratory infections (ARI) are pathologies that affect the respiratory tract from the proximal pharynx to the lungs, with an evolution of less than 15 days. They constitute the most frequent cause of morbimortality in the world. With the purpose of identifying the viral agents associated to this type of infections in patients of Zulia State, Venezuela, between February 2005 and July 2006, a total of 102 samples of the respiratory tract (oropharyngeal swab, nasopharyngeal swab, nasopharyngeal washing, spit and bronchoalveolar lavage) were studied. Viral isolation was made through a cellular culture and the identification of the pathogenic agents by the technique of direct immunofluorescence. Forty six positive samples were obtained (45%). The greater incidence was found in the groups of 41 to 64 years old patients, followed by lactanting babies (1 to 23 months). There were no significant differences between sexes. Within the isolated viral pathogens, Respiratory Syncytial Virus (RSV) was the agent most frequently found (32.6% p < 0.05), followed by Adenovirus (28.2%), Parainfluenza (23.9%) and Influenza (15.2%). The respiratory infections of the low respiratory tract were the most frequent (67.4%). A high incidence of associated viral agents to ARI in Zulia State is demonstrated. A high incidence in adult patients and the greatest positivity was found for RSV.