Chronic Granulomatous Disease (CGD) is a primary immunodeficiency characterized by an unusual predisposition to develop bacterial and fungal infections due to a failure of phagocytic leukocytes to generate superoxide, required for the intracellular killing of microorganisms. The lack of superoxide production is secondary to a defect in the NADPH-oxidase enzymatic complex activation, as a result of mutations of any of the components. Both, X-linked and autosomal recessive patterns of inheritance have been demonstrated in this disease, being the X-linked the most frequent and characterized by mutations in gp91phox. Mutations in p47phox, p67phox and p22phox have been shown in the autosomal recessive pattern. The molecular and genetic characteristic of NADPH-oxidase complex and its pathology in CGD are reviewed along with a brief description of the preliminary findings in two families from Mérida, Venezuela.