Upward flame spread on wall linings is analyzed theoretically with special emphasis on the application of the models to predict whether the flame spread will be deceleratory or acceleratory. Much of the work is devoted to a revised application of the model by Saito et al. By applying carious analytical expressions for the rate of heat release, quantitative expressions for the flame spread velocity are derived. Criteria for accelerating flame spread are presented. Due to the lack of large-scale flame spread tests, the predictions are compared with material data and room fire test results in Swedish BRANDFORSK test series on wall lining materials and in the EUREFIC programme.