Solid-solid reactions of an acidic clay and organoamines were investigated to obtain organophilic days. The reaction is based on the acid-base reaction between the acidic cite in the interlayer space of the clay and the organoamines (n-octadecylamine and oleylamine). The reactions gave organophilic clays identical to the organoammonium clays prepared by a conventional ion exchange reaction, with organoammonium chloride in aqueous media. Due to the simple and environmentally benign nature of the solid-solid reactions, the present reactions and the products are applicable to industrial uses. In addition, oleylamine gave better results in terms of viscosity of the suspension if compared with that of the n-octadecylamine system, showing the important roles,of surfactant molecular nature on the properties of organophilic clays.