Ecthyma gangrenosum is characterized by necrotic ulcerations surrounded by an erythematous halo. It is secondary to Pseudomonas aeruginosa infection. Most lesions are located in the anogenital and axillary areas, but the route of infection is generally difficult to establish. We report six children with perineal ecthyma gangrenosum and discuss predisposing factors, origin, and route of infection. This was a retrospective clinical study. Three children had blood cultures positive for P. aeruginosa, and one died. Predisposing factors were present in all cases; two had received chemotherapy (neuroblastoma, acute lymphoblastic leukemia), and two had idiopathic granulocytopenia. The last two patients previously had received treatment with systemic antibiotics and had abnormal granulocyte killing several months later. Septicemic ecthyma gangrenosum can be rapidly fatal in young children and requires aggressive antibiotic therapy. Benign ecthyma gangrenosum in healthy infants may result from a modification of bowel microflora after antibiotic therapy in conjunction with maceration in the diaper area. However, careful evaluation and long-term follow-up must be done to detect neutropenia, functional abnormalities of granulocytes, or a possible immune deficiency.