The use of conjugated org. compds. in fluorescence sensing applications was demonstrated to provide an impressive method to detect energetic nitro-arom. compds. The amplified fluorescence quenching in conjugated polymers was used for trace detection of nitro-aroms. This method, under one-photon excitation, possesses certain limitations such as the use of harmful ultra-violet radiation and relatively high background noise from light scattering. A novel approach that utilizes the addnl. benefits of nonlinear optical methods involves multiphoton excited fluorescence. This technique employs IR excitation which is essential for eye-safety applications and allows for deeper penetration through the atm., with relatively low background noise. Two conjugated polymers are reported which show good multiphoton absorption properties. This is combined with the excellent sensitivity of the multiphoton excited fluorescence to the presence of tri-nitro toluene (TNT). The multiphoton absorption cross-sections are provided and the Stern-Volmer plots are discussed. This technique, in combination with the great analyte sensitivity of various org. materials, promises to be an important sensing technol. in the IR spectral regions. [on SciFinder(R)]