Understanding the molecular mechanisms of cell-solid surface interactions is crucial for developing specific therapeutic strategies to control or modulate processes such as thrombosis, inflammation and cancer metastasis. In the vasculature or in blood contacting artificial devices these interactions occur under dynamic flow conditions. Primary adhesion or tethering of the flowing cells requires very special properties of the cell surface receptor and its ligand on the solid structure because of the very short contact times available for bond formation and the forces on those bonds due to fluid drag. Leukocytes utilize primarily members of the selectin family of receptors and their carbohydrate ligands for this first step - often resulting in a rolling interaction. For lymphocytes and monocytes, the integrin @alpha@@sub 2@ @beta@@sub 1@ is also capable of mediating primary adhesion under some flow conditions via its ligand vascular cell adhesion molecule (VCAM). Platelets utilize a receptor complex GPIb-IX-V for this tethering process. Secondary or firm adhesion is mediated by members of the integrin family on the cell surface, often after activation, in concert with their ligands on the solid. For leukocytes these are members of the @beta@@sub 2@ integrin family, while for platelets they are members of the the @beta@@sub 3@ integrin family. Methods for dissecting the specific molecular pathways involved for each step in the adhesion process for several cell types are given and the current state of our knowledge and potential applications are discussed.