Severe congenital neutropenia (SCN) is a rareE primary immunodeficiency disorder characterized by early onset recurrent infections in association with persistent severe agranulocytosis. To identify the clinical, immunohematological, and molecular characteristics of patients with SCN, 18 Iranian patients with the mean age of 8.8 +/- 5.8 years were investigated in this study. All of these patients experienced severe neutropenia; the mean of absolute neutrophil count was 281.4 +/- 137.7 cells/mm3. Bone marrow findings were typified by a myeloid maturation arrest at the promyelocyte-myelocyte stage in these patients. Molecular analysis revealed different mutations in the ELA-2 gene of one patient and in the HAX-1 gene of another three patients. The most common presenting complaints in these patients were superficial abscesses, oral ulcers, cutaneous infections, omphalitis, and pneumonia. During the course of illness, all patients developed mucocutaneous manifestations, and 16 cases had respiratory infections. The most commonly manifestations were abscesses, oral ulcers, pneumonia, periodontitis, otitis media, cutaneous infections, mucocutaneous candidiasis, and acute diarrhea. Three patients died because of a severe infection. Although SCN is a rare disorder, early onset of severe and recurrent infections should always raise a suspicion, which deserves further evaluation for detecting such disorder.