Polyamideimides having nonlinear optical (NLO)-active chromophores were synthesized by direct polycondensation of 4-[N,N＇-bis(2-aminoethyl)amino]-4＇-nitrostilbene (DANS-diamine) with oxy-bis[N-(4-phenylene)trimellitic imide] (BCI), N-(3-carboxyphenyl)-trimellitimide (BTI) and trimellitic anhydride chloride (TMAC). The direct polycondensation of NLO polyamideimides without a curing step may ameliorate the optical property of NLO polymers by reducing the optical propagation loss. The resulting polymers were highly soluble in aprotic polar solvents such as DMF, DMAc, NMP, etc. The NLO polyamideimides exhibited the inherent viscosity range of 0.14-0.33 dl g(-1). Molecular structural characterization for the resulting polymers was achieved by H-1 n.m.r., FTi.r. and u.v.-visible spectroscopies. The glass transition temperature for the resulting NLO polyamideimides was in the range 142-224 degrees C and they showed thermal stability up to 260 degrees C. The polymer solutions could be spin coated onto indium-tin-oxide (ITO) glass or quartz disc substrates to form optical quality thin films. The electro-optic coefficients (r(33)) at the wavelength of 1.3 mu m, measured by a simple reflection method, for polymer thin films poled around the glass transition temperature were in the range 1.9-7.4 pm V-1.