Organotin(IV) chemistry, with particular emphasis on solid-state structure and applications of ^ ^ m Sn MBssbauer spectroscopy to structural characterisation, is briefly reviewed. The relevance of structure to the biocidal properties of organotin compounds is also discussed. The results of variable-temperature 119m Sn MBssbauer spectroscopic (v.t.M.s.) studies of a range of phenyl- and cyclohexyl-tin compounds are reported and analysed. This technique provides a measure of the vibrational freedom of the tin atoms in a lattice and the results are interpreted in terms of the potential of the technique for distinguishing between monomeric and polymeric lattices and between the different three-dimensional conformations of the polymer chains observed in organotin chemistry. The solid-state structures of the pair of carboxylates triphenyltin acetate and triphenyltin formate have been determined by X-ray diffraction. In both compounds the carboxylates act as bridging groups to form infinite onedimensional polymeric chains with trans-O^SnPh^ geometry at tin. However, in triphenyltin acetate, the carboxylate group, as well as coordinating intermolecularly, also weakly chelates intramolecularly to give a six-coordinate tin atom - an unusual coordination number for a triorganotin compound. The polymeric chains are helical for both compounds, but a detailed consideration of their structures explains the observed significant difference in the v.t.M.s. behaviour of the two compounds. The crystal and molecular structure of dicyclohexylt in dichloride has been solved by X-ray diffraction. The chlorine atoms act as bridging groups linking the molecules intoaone -dimensionalpolymer, the local geometryattin being a severely distortedtrans -R^SnX^ octahedron. The structure substantiates aninitial prediction mode on the basis of the variable- temperature MBssbauer study of cyclohexyltins. On the basis of v.t.M.s. and other spectroscopic data structuralin ferences are drawn for a number of crystallographically unconfirmed phenyl- and cyclohexyl- t in compounds. It is a lsosuggested that for tricy clohexylt in compounds linear polymers rather than the more commonly observed zigzagor helical polymers a refavoured because of the steric bulk of the cyclohexyl groups. A preliminary v.t.M.s. study of tin -phthalocyanine complexes in dicates that this technique can distinguish between a monomeric lattice and one in which the complexes are linked by strong covalent bonds. It may thus be a useful tool in the study of electroactive materials based on metalloph thalocyanine species.