A three-dimensional integral equation theory is solved on a cubic grid to calculate the interaction entropically induced between big bodies with high asphericity immersed in small spheres. The interaction between big spherocylinders is analyzed along some representative trajectories and the physical origins of the results are discussed by referring to the packing of small spheres within the confined geometries. It is argued that the interaction between big, highly nonspherical bodies (e.g., cylinders, discs, and rectangular solids) exhibits interesting aspects which are not found in the interaction between big spheres. (C) 2003 Elsevier B.V. All rights reserved.