This technique is relevant to arson cases in which investigators wish to compare an ignitable liquid found in the fire debris with a liquid found in a suspect's possession, so as to determine whether the two samples of liquid may have come from the same source. Gasoline is the ignitable liquid found in a large percentage of arson cases. Gasoline from different sources may be distinguished by chemical conversion methods, treatment and reformulation processes, blending, and storage. In addition, once a new shipment of gasoline is sent to a fueling station, the new batch of gas is mixed with the residual gas still in the storage tanks, thus creating a unique blend. The current study used GC-MS and the sequential peak ratio method developed by Dolan and Ritacco to compare the headspace of evaporated gasoline extracted from fire debris with the headspace of the source gasoline, which had not undergone evaporation. The materials and methods as well as data analysis are described in detail in this paper. The study found that 50-percent and 75-percent evaporated gasoline samples both contained similar ratios of certain components when compared with the unevaporated source gasoline. Thus, in cases that involve gasoline evaporated up to 50 percent and extracted from pine, it is possible to eliminate comparison samples as coming from the same source. The results of the 75-percent comparison indicate that it may be possible to use the same type of comparison to cases that involve 75-percent evaporated gasoline. 6 figures, 1 table, and 7 references