An overview of inclusion phenomena, both in the solid state and in solution, is given. Following this orientating survey, a study of the systematic modification of some selected hexahosts is described. The versatile hexahost hexakis(benzyl-thiomethyl)benzene was chosen for detailed study. Substitution of each of the six outer aromatic rings was found to give a series of hosts with wide-ranging inclusion behaviour and differing guest selectivities. General inclusion properties have also been established for hexakis(2-phenylethylthiomethyl)-benzene, the first hexahost possessing a four atom inter-ring chain. An X-ray analysis of the 1,4-dioxan adduct of hexakis-(benzylthiomethyl)benzene has revealed a true clathrate structure for this material.