A recently developed technique for the measurement of cell migration on surface bound gradients was used to assay the behavior of microvascular endothelial cells on a range of fibronectin gradient slopes in the presence of soluble promoters and inhibitors of chemotaxis. Directional microvascular endothelial cell migration was shown to increase with increasing gradient slope with no significant change in cellular persistence time or random cell speed. Uniformly distributed soluble chemotactic factor in the hMEC growth media enhanced directional migration. The addition of migrationinhibiting LY294002 eliminated the directional component of cell migration at a 5 μM dosing. These experiments broaden the understanding of the directional nature of cell motion and present a reliable system for the quantitative study of cell migration in complex conditions in vitro.