Bi4Ti3O12 thin films have been grown on indium-tin-oxide coated glass by pulsed laser deposition. Films are rapidly thermal annealed at 650°C in three kinds of atmospheres such as O 2, N2, and air. The annealing atmosphere is found to be an important growth parameter which determines the crystallization, microstructures, and the leakage current behaviors. The film annealed in oxygen has a columnar grain structure with an amorphous phase, and its leakage current behavior is in agreement with the prediction of the space-charge-limited conduction model. The film annealed in nitrogen has polycrystalline porous structure, and its high field conduction is well explained by the thermoionic emission model, called the Poole-Frenkel emission. On the other hand, the film annealed in air has both the columnar and porous structures, and its electrical behavior shows characteristics of both models.