Epitaxial thin films of PrBa2(Cu0.8Al0.2)(3)O-7 have been vacuum deposited by rf sputtering on the LaAlO3 substrates. Though electrically much more resistive, these Al-substituted films are all of orthorhombic structure and epitaxial quality on various oxide substrates, much like YBa2Cu3O7 and PrBa2Cu3O7 grown under similar conditions. The samples appeared to be shiny and dark as observed with the naked eye, but their electrical resistivity, rho(T), ranged from similar to1 Omega cm at room temperature to about six orders of magnitude higher at Tsimilar to30 K. From the rho(T) functional for both the target and the films, which, by and large, follows Mott's T-1/4 law with their own relevant material constants, we believe that the mechanism of electrical conduction was mainly through variable range hopping. This suggests that the substitution of Al has caused extensive localization of charge carriers. The localization radius is similar to0.2 nm while the hopping distance is similar to3-9 nm. (C) 2002 American Institute of Physics.