Pseudomonas aeruginosa, is an opportunistic organism widely distributed in both environmental and nosocomial settings. Invasive infections typically occur in immunocompromised patients, but this agent can also produce sepsis in the immunocompetent host. We report the case of an 8 months old infant, previous healthy, who presented septic shock by P aeruginosa. Lesions of ecthyma gangrenosum in his limbs required surgical debridement. The patient presented transitory neutropenia and reduced C-4 levels but subsequent study of immune defects was normal.