This paper describes the photorefractive properties of a new and growing class of materials exhibiting the effect, doped nonlinear organic polymers. We show directly using a PMMA-based copolymer with a pendant nonlinear nitroaminotolane chromophore doped with a charge transport agent that the presence of photoconductivity and optical nonlinearity are only necessary, but not sufficient to guarantee that a given materials system will yield measurable photorefractive gratings, rather than gratings due to some other process such as photochromism. To prove photorefractivity unequivocally, direct measurement of the spatial phase shift between the intensity pattern and the index modulation is best, and we summarize a convenient way to do this using two-beam coupling and sample translation. In addition to the photorefractive epoxy materials such as bisA-NPDA:DEH reported earlier (Phys. Rev. Lett. 66, 1846 (1991); Proc. SPIE
1560, 278 (1992)), a new PMMA-based copolymer with pendant p-nitroaniline chromophores doped with DEH also shows photorefractive grating formation, with writing speed 100 times higher than that for the epoxy material.