Abstract: A vermiculite-aniline intercalate with a basal spacing of 14.78 Å was investigated by one- and two-dimensional X-ray diffraction methods. The intercalate, prepared by ion exchange between Na-saturated vermiculite from Llano, Texas, and a 1% aniline hydrochloride solution, contains only one aniline cation per single layer cell. A reduced effective cell-charge is believed to be responsible for this. Structure factor calculations were made in space group C2/c and with unit cell dimensions of a = 5.33, b = 9.18, c = 29.78 Å and β = 97.0°. However, extra reflections in the a*b* plane, which are similar to those in a vermiculite-benzidine intercalate, showed that after aniline intercalation the true unit cell became primitive. The aniline cations are distributed statistically over equivalent crystallographic sites in the interlayer space. The organic molecules are orientated with their planes vertical and their nitrogen atoms over the projected centers of the ditrigonal cavities into which they key. The aniline cations form ordered arrays upon the silicate layers by packing into rows. Perpendicular to , populated and vacant rows alternate. Along populated rows aromatic ring planes are alternately parallel and perpendicular to . With small adjustments this model is similar to that of benzidine-vermiculite.