Neutrophil migration into infected tissues is essential for host defense, but products of activated neutrophils can be quite damaging to host cells. Neutrophil influx into the lung and airways and resultant inflammation characterizes diseases such as chronic obstructive pulmonary disease (COPD), bronchiectasis, and cystic fibrosis. In order to migrate, neutrophils must re-organize the actin cytoskeleton to establish a leading edge pseudopod and a trailing edge uropod. The actin binding protein Myristoylated Alanine-Rich C-kinase Substrate (MARCKS) has been shown to bind and cross-link actin in a variety of cell types and to co-localize with F-actin in the leading edge lamellipodium of migrating fibroblasts. The hypothesis that MARCKS has a role in the regulation of neutrophil migration was tested using a cell permeant peptide derived from the MARCKS myristoylated aminoterminus (MANS peptide). Treatment of isolated human neutrophils with MANS significantly inhibited both their migration and 2 integrin-dependent adhesion in response to fMLF, IL8, or LTB4. The IC50 for fMLF-induced migration and adhesion was 17.1 µM and 12.5 µM, respectively. MANS significantly reduced the F-actin content in neutrophils 30 sec after fMLF stimulation, although the peptide did not alter the ability of cells to polarize or spread. MANS did not alter fMLF-induced increases in surface 2 integrin expression. These results suggest that MARCKS, via its myristoylated aminoterminus, is a key regulator of neutrophil migration and adhesion.