Polycrystalline thin films often develop residual stress during growth. Since it can be large enough to impact performance or cause failure, there is a need to understand and control it. Stress evolution can be measured in real-time during film growth using wafer curvature techniques. A large number of studies have been performed that quantify the dependence of the stress on deposition rate, grain size, temperature and microstructure in numerous materials systems. These show that the residual stress may depend strongly on the processing conditions, e.g., electrodeposited Ni films can be 400 MPa (tensile) if the film is grown rapidly and -500 MPa (compressive) if the film is grown slowly. The stress can also go through a series of states during deposition, even changing sign as the microstructure evolves from individual islands to a continuous film.