Progress made on NIST Grant No. 60NANB4D0037 is reported here. Since the three previous annual reports describe the work conducted in the first three years, the scope of this report is limited to the past (and final) year of the grant, in which a study of upward flame spread on vertical walls was conducted. First, a detailed review of literature on upward flame spread is presented. A "complete procedure" for predicting upward flame spread on practical materials, which can be used in a global fire hazard assessment model, is then described. Experimental results on upward flame spread on various materials are obtained, and the validity of the model is established.