We report the effect of pulmonary passage on random migration and chemokinesis of neutrophils through capillarylike pores under the in vitro condition of Boyden's test. Neutrophils were isolated either from the left ventricle or from the pulmonary artery of patients who underwent coronary angiography due to suspected angina pectoris or valvular heart disease. In all 14 cases left ventricle neutrophils showed significantly enhanced chemotactic-activated migration compared with pulmonary artery neutrophils. Pulmonary passage also influenced the random migration of neutrophils, except for those derived from five patients suffering from pulmonary hypertension. Our findings might indicate that accumulation of neutrophils in the capillaries of the normal lung is counteracted by a change in neutrophilic migration behavior during pulmonary passage, thus avoiding increased neutrophilic sequestration in pulmonary microcirculation as observed in adult respiratory distress syndrome.