The 60 MHz1H NMR spectra of paramethadione, 5-ethyl-3,5-dimethyl-2,4-oxazolidinedione,1, have been studied at 28° in CDCl3solution with the achiral reagent tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III),2, and the chiral reagents tris[3-(trifluoromethylhydroxymethylene)−(+)-camphorato]europium(III),3, and tris[3−(heptafluoropropylhydroxymethylene)−(+)-camphorato]europium(III),4.SubstantiaΔδ values and spectral simplification are achieved with2or4. Significant enatiomeric shift differences, ΔΔδ, are observed with 4 that should provide direct optical purity determinations of − 1, using the C(5)CH3 or the NCH, signals with &:Iratios of 1.3–1.5. Valley height for the CCH, resonance as low as 4.8% was achieved, which should allow detection of as little as 3–4% of the minor enantiomer. Results are discussed in terms of the structural features of I and of the LSR. Substantial nb values and spectral simplification