Single crystal X-ray crystallography can be applied to the entire spectrum of molecular size. If performed correctly the result is an unambiguous, three dimensional image of all the atoms located within a molecule. This applies to small chemical structures all the way through to biological macromolecules.In this thesis the method is used to solve the crystal structures of four small molecules and in addition to two macromolecular adducts.The first two molecules studied were believed to be closely isomorphous cobalt containing structures. The first small molecule was found to be C26H36N 8018Cl2Co and crystallised in the triclinic space group P1. The structure was solved with an R factor of 0.0309. The second small molecule was found to be C26H36N8O 10F12P2Co and crystallised in the triclinic space group P1. The structure was solved with an R factor of 0.0313.The remaining two small molecules were believed to be closely isomorphous tin containing structures. The third small molecule was found to be Ph4Sn and crystallised in the tetragonal space group P421/c. The structure was solved with an R factor of 0.0353.The fourth small molecule was found to be C30H24 NO4Sn and crystallised in the triclinic space group P1. The structure was solved with an R factor of 0.0245. In addition the crystal packing of all four small molecules were analysed. The implications of the determined crystal structures are discussed in terms of the relevant literature in each case.The method was also used to determine the structure of two macromolecular adducts. The first was a co-crystallisation of hen egg white lysozyme and Ta6Br12. The model refinement and a description of the Ta6Br 12 binding sites are included.The second was a co-crystallisation of hen egg white lysozyme and carboplatin with the solubility of the carboplatin optimised using DMSO, whilst still obtaining crystals. The model refinement and a description of the carboplatin binding sites are included.Finally conclusions and possible routes for future work are offered.