An investigation of the gasoline permeation resistance of the as-blow-molded and annealed polyethylene, polyethylene (PE)/polyamide (PA), and polyethylene/modified polyamide (MPA) bottles is reported. The gasoline permeation resistance improves dramatically after blending PA and MPA barrier resins in PE matrices during blow-molding, and the order of barrier improvement corresponds to the order of barrier improvement of the barrier resins added in PE. Somewhat unexpectedly, the gasoline permeation rates of the annealed PE and/or PE/PA bottles annealed at 90 degreesC or higher temperatures increase significantly with the annealing temperature and time. On the contrary, the gasoline permeation resistance of the annealed PE/MPA bottles increase significantly as the annealing temperature and/or time increase. For instance, the gasoline permeation rate of the PE/MPA bottle annealed at 120 degreesC for 32 h is about 190 times slower than that of the as-blow-molded PE bottle. Further investigations found that, after blending the MPA and PA barrier resins in PE matrices, the relatively nonpolar hydrocarbon components present in the gasoline fuels were significantly blocked, without permeation during the permeation tests, in which the as-blow-molded PE/MPA bottle inhibited the permeation of hydrocarbon components more successfully than did the as-blow-molded PE/PA bottle. In contrast, the amounts of polar components that permeated through the as-blow-molded PE/PA and PE/MPA bottles were very small and about the same as the amount that permeated through the as-blow-molded PE bottle. Possible mechanisms accounting for these interesting behaviors are proposed in this study.