Diorganotin(IV) derivatives of chloramphenicol, {=D-(-)threo-2,2-dichloro-N-[ β-hydroxy- α-(hydroxymethyl)- β-(4-nitrophenyl)ethyl]acetamide (=Hchloramph)}, and D-cycloserine, {=(R)-4-amino-3-isoxazolidone [=Hcyclos]} have been prepared. The stoichiometries of the obtained compounds were R 2SnClantib and R 2Snantib 2 (antib −1=chloramph −1, R=methyl and phenyl; antib −1=cyclos −1, R=methyl). The solid state configuration of the complexes was investigated by I.R. and Mössbauer spectroscopy, from which structural hypotheses were inferred. In particular, the experimental data suggested monomer structures both for R 2Sn(IV)Clchloramph and R 2Sn(IV)chloramph 2, in which chloramphenicolate anion behaved as monoanionic monodentate ligand through the oxygen atom of the deprotonated secondary alcoholic group, with formation of tetrahedral R 2SnOCl and R 2SnO 2 environments. In R 2Sn(IV)Clcyclos and R 2Sn(IV)cyclos 2 derivatives, Mössbauer spectroscopy, and in particular the narrowness of the full width at half height of the resonant peaks, Γ 1 and Γ 2, suggested the occurrence of two different absorbing tin sites with different environments around the tin(IV) atoms. According to calculations performed by applying the point charge model formalism, one site was constituted by a tin(IV) tetrahedrically coordinated by monoanionic monodentate cycloserinate groups, through the oxygen atom of the resonance stabilised hydroxamate anion, originating R 2SnClO and R 2SnO 2 polyhedrons both in R 2Sn(IV)Clcyclos and R 2Sn(IV)cyclos 2, respectively. The second site would correspond to a tin(IV) in a polymeric octahedral configuration with Me 2SnCl 2ON and Me 2SnO 2N 2 environments, in Me 2Sn(IV)Clcyclos and Me 2Sn(IV)cyclos 2 derivatives, respectively, in which the second donor atoms was the amino nitrogen atom. 1H and 13C NMR spectra, of both chloramphenicol and its diorganotin(IV) derivatives were carried in DMSO-d 6 solution, in which R 2Sn(IV)Clchloramph and R 2Sn(IV)chloramph 2 underwent total, (R=Me), or partial, (R=Ph), dissociation. As far as the organotin(IV)-D-cycloserine derivatives were concerned, 1H and 13C NMR spectra, also carried out for the free D-cycloserine, showed that, owing to the coordinating properties of the solvent, octahedral and trigonal bipyramidal isomers were present in DMSO solution of Me 2Sn(IV)Clcyclos and Me 2Sn(IV)cyclos 2. Finally, the cytotoxic activity of the free chloramphenicol, D-cycloserine and of their dimethyltin(IV) derivatives has been investigated towards Ciona intestinalis and Ascidia malaca fertilised eggs, at different developing stages.