Pertussis is one of the leading causes of death that can be prevented by vaccination. More than 600,000 deaths from pertussis occur annually, with a disproportionate number appearing in unvaccinated infants. Pertussis is particularly troublesome because it does not necessarily present itself in its commonly known classical stages. Therefore, in very young and non-immunized children, the disease may have a fulminant process characterized by severe leukocytosis, neurologic involvement and serious cardiopulmonary failure that can be accompanied by pulmonary hypertension, persistent hypoxia and death. This article describes two infants with fulminant pertussis; they were admitted for acute respiratory failure and severe leukocytosis and ultimately died from multi-organ failure.