Several solvent systems used in conjunction with silica and base-treated silica plates have been proposed for the analysis of amphetamines and methylamphetmine; however, it was important for this study to select a system that would provide separation of these drugs and provide reproducible Rf data; therefore, a number of TLC systems, together with some modifications, were evaluated. To determine which of two resulting systems gave the better precision, 10 replicate analyses were performed for each of the drug samples. With Fast Black K (FBK) salt it was possible to discriminate between primary amines (for example, amphetamines) and secondary amines (for example, methylamphetamines) by their different colored derivatives. A TLC solvent system that consisted of methanol:acetone:ammonia (100:24:1.6) was found to give reproducible Rf data for these drugs. The optimum reaction conditions were determined for the derivatization procedure by isolation and identification of the products. These conditions provided minimum detection levels of 50 ng for amphetamine and methylamphetamine. 4 figures, 5 tables, and 4 references