The complexes of the cycloserine derivative, 4,4'-[1,4-phenylenebis(methylidynenitrilo)]bis(isoxazolidin-3-one) or terizidone, with chromium(III), ruthenium(III) and rhodium(III) have been synthetized; their structures have been suggested on the basis of analytical, conductivity, spectral (visible, infrared and far-infrared) and magnetic data, and the thermal analyses have revealed the extent of coordinated water among the chromium and ruthenium complexes. The various ligand field parameters have been evaluated; the B' values suggest a strong covalency in the metal-ligand σ bond and the Dq values show a medium-strong ligand field. The position and multiplicity of the metal-halogen stretching modes in the far-infrared region have been extensively investigated and discussed; the results are particularly useful in distinguishing between the mer- and fac-isomers in the octahedral compounds of the ML3X3 type. The ligand is monodentate O-bonded or N-bonded through the oxygen of the keto group or through the nitrogen of the imino group of the isoxazole ring. We have never observed a metal-induced cycloserine ring opening under the present experimental conditions.