Traction Microscopy Quantification of contractility and adhesion of living cells in culture is essential in understanding of mechanotransduction in a variety of cell functions, including contraction, spreading, crawling, and wound healing. Using the deformable gel substrate technique, we measure displacements of small (0.2mm diameter) fluorescent beads during contraction of plated cell challenged by varying doses of contractile agent. The traction field is computed from the displacement field at the cell-gel interface. The average stress within the cell is calculated from the traction field. These findings are used for development of mechanistic models of cell function that emerge from collective interactions among different cytoskeletal filaments and extracellular adhesions in living cells.