It is pointed out how infections can delay growth and development through an aggressive and long-standing action, through direct action of an infecting agent (virus, bacteria, parasites). or through sequelae in main organs (brain, kidney, growth cartilage, muscular system, etc.). how infections impair nutrients' absortion, metabolism and excretion. The role of the leukocytes is evidenced in the liberation of two factors: MEL and pyrogen factor. Metabolic responses are classified in an anabolic anda catabolic phase. The second mechanism that interfers on growth and development is a specific action of various agents, particularly viruses on different tissues. Intrauterine infection is pointed out as determinant of growth disorders with increased IgM levels in cord blood; confirmed fetal infection on the 6th up to 8th week of gestation interferes with organogenesis. The action of CMV and rubella virus is mentioned as example. The action of viral infections on growth during the first three months of gestation, is mentioned. TBK and typhoid fever are mentioned as causative agents of corporal and urinary nitrogen loss. Negative action of infection on growth and development, particularly in malnourished patients, is discussed. Diarrhea, under certain condition, is pointed out as determinant of the kwashiorkor syndrome. The role of various parasite diseases on growth is mentioned with range according to the action of each agent on nutrients' absortion. A third mechanism which causes fail to thrive through sequelae lesions is considered. This disorders are ruled by the age of the patient with the onset of disease by the causative agent, by the inflammatory process involved, by the early diagnosis and appropriate treatment. The need of enhancing the actions to prevent communicable diseases and to diminish malnutrition rates is pointed out and the significance of taking into account calorie and protein intake in patients with severe and/or long-standing infectious disease.