We have examined the possibility that mouse bone marrow-derived cultured mast cells (BMCMC) have the capacity to attach to and migrate on extracellular matrix components in vitro through the use of time lapse videography. Unactivated mast cells did not display significant interaction with slide flasks coated with either 3% BSA or collagen IV, and FcεRI-mediated activation of BMCMC did not appreciably increase their attachment and migratory characteristics. Both activated and unactivaled BMCMC adhered to surfaces coated with a synthetic IKVAV laminin polypeptide, but this association resulted in the immobilization of the cells to the substrate. BMCMC did not adhere to surfaces coated with laminin, fibronectin or matrigel until Fcε RI-mediated activation, after which they displayed rapid, random movement on these surfaces. Cells continually interacted with laminin. fibronectin or matrigcl by flattening, interspaced by periods of movement as rounded cells with small pseudopodia. The mean velocity of BMCMC on laminin, fibronectin or matrigel was similar and averaged approximately 180 μm/hr. The mean velocity of BMCMC on these three substrates was not significantly different from the mean velocity of monocytes on laminin. The movement of BMCMC on these substrates demonstrated a directional tendency. In summary. these results demonstrate that mast cells activated through FcεRI are capable of attachment to and motion on components of extracellular matrix, and demonstrate one mechanism by which mast cells may migrate to areas of inflammation and wound repair.