Inclusion compounds are typical representatives of guest-host systems and serve as models in the field of molecular recognition. They consist of an almost rigid host lattice with channel- or cage-like cavities which are able to incorporate various guest molecules of quite different chemical structure (cycloalkanes, linear alkanes, polymers). Our present activities are focussed on the characterization of the guest components in these systems. At present, various types of inclusion compounds (host components: urea, thiourea, cyclophosphazenes, cyclodextrins and tri-o-thymotide) are examined in which guests, such as substituted cyclohexanes, six-membered ring systems and n-alkanes, are incorporated. The various complexes are characterized by differential calorimetry in order to determine the actual phase behaviour. Afterwards, dynamic solid state NMR spectroscopy is used to provide quantitative data about the molecular order (absolute orientation of the guests, orientational disorder, conformational order) and dynamics (conformational, reorientational and lateral motions) of the guest species over a large temperature range, that might reach from 5 K to 380 K. So far, primarily ²H NMR investigations are performed on inclusion compounds with selectively deuterated guest compounds. The molecular parameters can be obtained from the analysis of variable temperature lineshape studies, relaxation and 2D exchange experiments employing suitable simulation programs. From this, there is access to molecular motions that can cover several orders of magnitude. In addition, ¹³C MAS NMR and FT IR spectroscopy is used for the evaluation of the conformational properties of these systems. It is found that both the molecular dynamics and the molecular order are strongly affected by the surrounding host matrix. In particular, this can be seen by the changes of the guest properties in the vicinity of solid-solid phase transitions which usually are accompanied by a distortion of the host lattice. The above investigations also provide information about non-bonded interactions between the various species in such guest-host systems.