The direct determination of both the optical purity and absolute configuration of threo-methylphenidate has been accomplished in a simple, specific, and accurate manner by 1H-NMR spectroscopy. The enantiomeric resonances of threo-methylphenidate were effectively resolved in CDCl3 solution by the addition of the chiral solvating agents (R)-(-)- or (S)-(+)-2,2,2,-trifluoro-1-(9-anthryl)ethanol. Optical purities were determined on the basis of the intensities of the enantiomeric ester methyl proton resonances; the assignment of enantiomeric configurations was based on the relative field positions of these resonances and the examination of molecular models. The analysis of synthetic enantiomeric mixtures of threo-methylphenidate by the proposed NMR method resulted in assay values that agreed closely with the known quantities of each enantiomer in the mixtures tested. The mean +/- SD recovery value for the (2S,2'S)-(-)-threo-enantiomer, amounting to 99.9 +/- 0.6% of added (n = 10), correlated well with that previously found by 1H-NMR spectroscopy with a chiral Eu(III) shift reagent. However, the present approach is simpler, shows less reliance on reagents and solvents of a high purity, and does not require strict anaerobic working conditions.