An 18-month-old infant with delayed separation of the umbilical cord and severe recurrent bacterial infections since the newborn period was found to have depressed polymorphonuclear leukocyte locomotion and oxidative metabolic response to particulate stimuli. Both her polymorphonuclear leukocytes and monocytes demonstrated a markedly delayed chemiluminescence response to zymosan, but there was a normal chemiluminescence response to soluble stimuli, phorbol myristate acetate and calcium ionophore A23187. The patient also had a marked delay in uptake of Staphylococcus aureus and Escherichia coli. The patient's polymorphonuclear leukocytes were normal morphologically, and myeloperoxidase was present in histochemical stains. The dichotomy between normal oxidative response to soluble stimuli and abnormal response to opsonized particulate stimuli, plus abnormal cell locomotion and phagocytosis, suggest an abnormality of cell membrane fluidity or contractility.