Chronic granulomatous disease (CGD) is a syndrome, the unifying characteristics of which arc a predisposition to recurrent bacterial and fungal infections, an impaired ability of phagocytes to kill microorganisms and the failure of these cells to produce microbicidal oxygen metabolites. Four genetically different molecular defects have been found to underlie the x‐linked and autosomal recessive forms of CGD. Since the relevant normal genes are cloned, molecular analysis of the genetic lesions in CGD is rapidly progressing. Diagnosis of carriers is possible in most instances and prenatal diagnosis by trophoblast biopsy or at least cordoccntcsis is now feasible. Until recently, therapy has been limited to aggressive antimicrobial prophylaxis and in very selected cases bone marrow transplantation. A new development is the introduction of recombinant human interferon‐λ as infection prophylaxis. Finally, our current knowledge of the genetic defects in CGD may allow the development of somatic gene therapy directed at monocytes, or more permanently at bone marrow or peripheral blood stem cells, and promises definitive cure of this still life‐threatening disease.