Solid-state dye-doped polymers are an attractive alternative to conventional liquid dye solutions. In this paper, the spectral characteristics and nonlinear properties of the Aniline Blue dye has been studied. The third-order nonlinear optical properties of the Aniline Blue dye in ethanol and a dye-doped polymer film were measured by the Z-scan technique using a 632.8-nm He-Ne laser. This material exhibits a negative optical non-linearity. The dye at a 0.4-mM concentration exhibited a nonlinear refractive coefficient (n 2 = -4.02 × 10-8 and -4.41 × 10-8 cm2/W in liquid and solid media, respectively), a nonlinear absorption coefficient (β = -9.7 × 10-4 and -11.63 × 10-4 cm/W in liquid and solid media, respectively), and susceptibility (x (3) = 1.844 × 10-6 and 2.028 × 10-6 esu in liquid and solid media, respectively). These results show that the Aniline Blue dye has potential applications in nonlinear optics. © 2008 Pleiades Publishing, Ltd.