When pertussis is associated with hyperleukocytosis, mortality approaches to 80%. Immature leukocytes have been identified in pulmonary arterioles, small arteries and venules. Techniques aimed at reducing leukocyte mass might improve the prognosis of these patients. We report our experience with 3 patients in whom a leukoreduction was performed in the context of severe pertussis and hyperleukocytosis.