The peeling behavior of polyimide film coated on steel substrates was experimentally investigated and compared with existing models. An operating window for peeling, which is defined as a closed domain for steady and defect-free peeling, is presented in terms of peeling force versus residual solvent content. The window is bounded by two major defects: the film becomes too brittle for peeling at high peeling force, and stick-slip striation defect appears at low peeling force. There exists a critical residual solvent content below which the adhesion between the polyimide film and the substrate is too strong and then peeling is impossible. Existing models for predicting steady peeling and the onset of peeling defects have been modified and applied to setup the boundaries of the operating window. There also exists another operating window for drying of polyimide and is presented in the form of drying temperature versus film thickness. POLYM. ENG. SCI., 50:1128-1139, 2010. (C) 2009 Society of Plastics Engineers