CCL3 is a chemoattractant for both peripheral blood monocytes and alveolar macrophages. Freshly isolated monocytes and alveolar macrophages (4.5 × 104 per condition) were subjected to migration assays using increasing concentrations of rhCCL3 as the chemoattractant. Monocytes (filled bars) and alveolar macrophages (open bars) responded in a dose-dependent manner to CCL3 (1–100 ng/ml). Compared to unstimulated cells, cellular migration was significant (**p < 0.001) at all CCL3 concentrations tested, for both cell types. Additionally, the average number of migrating alveolar macrophages (maximal response = 13.0 ± 0.8 migrating cells per high-powered field at 10 ng/ml CCL3) was 4–6-fold less than the average number of migrating monocytes (maximal response = 77.2 ± 3.4 migrating cells per high-powered field, at 10 ng/ml CCL3) (p < 0.001 when comparing monocyte and alveolar macrophage migration at every concentrations of CCL3). The mean of six independent experiments ± SEM are shown.