This study also included epidemiologic data to determine the risk factors for the enhancement of these infections. The coagglutination technique for the rapid diagnosis of streptococcus was tried. Five hundred and thirty one samples of pharingeal swabs were obtained from children with ARI. 74% were younger than one year old. Brochopneumonias constituted 66.39% of the cases. In total 357 agents were isolated 35% corresponding to bacteria in pure culture, 23.3% to mixed infections and 11.6% only viruses. The bacteria were: Haemphilus influenza (12.4%), Streptococcus pneumoniae (11%), Staphylococcus aureus (9%), and Klebsiella pneumoniae (6.3%), Mycoplasma pneumoniae was identified in 5 children and M. hominis in 3. Adenoviruses were isolated in 98 patients, parainfluenza in 19, respiratory syncytial virus in 4, influenza in 1 and picornavirus in 2. Predominating socioeconomic factors were: overcrowding, deficient schooling and low income of parents which favor malnutrition. The more frequent agents were constitutes by bacteria. Viruses were a less cause of infection. It was confirmed that babies under 12 months are more susceptible to bacterial pneumonia and prompt treatment with antimicrobial agents lowered the lethality. Low socioeconomic level is a possible predisposing factor for respiratory diseases.