The rheological properties of liquid polybutadiene rubber/organo-clay nanocomposite gels were investigated by rheological experiments, focusing on the effects of clay exfoliation and orientation-disorientation, as well as polymer-clay interaction and temperature. Both irreversible and reversible viscosity transitions were observed in the temperature range from 26 to 136 ?C in steady shear experiments on as-prepared and exfoliated samples. These transitions depend strongly on the end-groups, molecular weight of the liquid rubber and on the shear field. The irreversible transition is attributed to the exfoliation of the clay, and the reversible transition can be understood as a shear-induced orientation-disorientation transition of the clay sheets. Polymer-clay interaction is confirmed to be a key controlling factor of the orientation-disorientation transition, whereas the shear field plays a critical role to induce such a transition. To our knowledge, this is the first rheological observation of the in-situ exfoliation process and the shear-induced orientation-disorientation transition of layered silicate in polymer/organo-clay nanocomposites. A tentative model was suggested based on the clay exfoliation and orientation-disorientation transition, and the model is used to explain the observed unique rheological behavior.