10.22376/ijpbs.2019.10.1.p1-12 Volume 12 issue 4 October - December Pneumonia, defined as inflammation of the lung parenchyma, which is the leading infectious cause of death globally among children younger than 5 years. The active form of vitamin D regulates more than two hundred different genes directly or indirectly binding to vitamin nuclear hormone receptors that derive a wide variety of biological processes and regulate cell proliferation, differentiation, apoptosis, and augment immune function. This study was designed to investigate any possible association between vitamin D level if it's below 10, between 10- 20,20- 30 or above 30 ng/ml, and the development of community-acquired pneumonia and the severity of the pneumonia with low vitamin D level . It was a case-control study carried out in Babylon Maternity & Pediatrics Teaching Hospital for the period from first of March till the end of July 2019, which involved one hundred patients with community-acquired pneumonia and fifty healthy children and their ages ranged from one month to 14 years old and vitamin D level was measured from the studied groups. This study revealed 76% of the patients with community-acquired pneumonia had inadequate levels of vitamin D and 12% had severe deficiency while in the control group the percent of severe deficiency of vitamin D was zero. Residency, type of feeding, and age group also had their influence on vitamin D level in this study as it had shown that vitamin D level was more deficient in breastfed than formula-fed patients, also it was lower in patients who are living in urban areas than those who live in rural areas and in patients below one-year-old had lower levels of vitamin D than those in other age groups. Also, there was a statistically significant relationship between low vitamin D and in patients with more severe pneumonia. This study revealed that vitamin D levels were lower in patients with community – acquired pneumonia than in the control group and including all whose levels of vitamin D were in severe deficiency. This study concluded that severe pneumonia is associated with severe deficiency of Vitamin D and the need for vitamin D supplementation as necessary. Prof. Dr. Yahya Altufaily, Lubna Mohammad Hussein and Dr. Fadhil Sahib Hassnawi Community-Acquired Pneumonia, Vitamin D Level, Pediatric. 47-52