Acute respiratory infections are the main cause of morbidity worldwide, and pneumonia represents one of the main causes of death in children younger than the age of 5 years in developing countries. Several risk factors for acquiring respiratory infections in developing countries, such as poverty, restricted family income, low parental education level, low birth weight, malnutrition, and lack of breastfeeding, have been described. Another important factor in recent years that has aggravated the problem of acute respiratory infections in developing countries is the human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) pandemic. In developing countries, identifying the etiology is difficult and World Health Organization recommends making the diagnosis of pneumonia based on clinical parameters. The diagnosis and suitable treatment administered by primary healthcare workers, particularly in rural areas, is part of the strategy to prevent mortality. Finally, it is important that industrialized countries support the economic growth of the developing countries to improve their healthcare system and to ensure that performed research studies will give benefits to their populations.