This research used the internal standards method of quantitative proton NMR. In this method, the integral of the analyte peak is compared with that of the integral of a pure internal reference material peak. This is important when a reference drug standard is not available or is costly. NMR can be used in the identification and purity determination of reference standards as well. Another advantage of NMR is that it does not have a medium (i.e., column), which can lead to solute adsorption effects and imprecise analysis. In addition, a wide variety of deuterated solvents are available, which enables quantitation of a large variety of drugs. So long as the drug of interest is fully soluble, does not interact with the solvent or internal standard, the internal standard is free of interfering signals, and the compound contains nonlabile hydrogens, an accurate quantitation is possible. This article describes the instrumentation and materials used in the analysis, including internal standard solution preparation, sample preparation, and quantitative performance. Results are presented according to accuracy and the determination of mixtures of seized drugs and related compounds. The linearity of the NMR probe was determined by using methamphetamine HCL dissolved in deuterium oxide with maleic acid as the internal standard (5 mg) for concentrations from 0.033 to 69.18 mg/ml, with a resulting correlation coefficient greater than 0.9999 for all six methamphetamine peak groups. The spectra of illicit heroin, methamphetamine, MDMA, and cocaine samples are presented, along with an extensive list of compounds, their solubilities, and the solvents and internal standard used. 1 table, 10 figures, and 14 references