BACKGROUND: Inflammatory cells may play a role in thrombus formation. However, the impact of monocytes in thrombosis and clinical characteristics of patients with monocyte-rich thrombus are less well understood. METHODS: A FeCl RESULTS: In 90 mice, CD68 (monocyte/macrophage) counts increased from 3 hours in a time-dependent manner, and decreased after 48 hours ( CONCLUSION: Monocytes/macrophages increasingly infiltrated the thrombus after a few hours in mouse arterial thrombosis model, suggesting their role in later stages rather than initial stages of thrombosis. Stroke patients with higher monocyte/macrophage counts had less frequent parenchymal hematoma and more frequent functional independence, suggesting that monocyte/macrophage-rich thrombi are a predictor of better clinical outcomes.