A thin-layer chromatograpy (TLC) method is developed to analyze artemisinin (AT) and its derivatives, artemether (AM) and arteether (AE), using a silica-gel plate with a mobile phase containing pure chloroform. After development, all products are visualized after dipping in a 4-methoxybenzaldehyde dipping reagent of 1% (v/v) in an acidic solution of sulphuric acid (98%, v/v) and acetic acid (96-98%, v/v) (respectively, 2% and 10%, v/v in alcohol-water, 60:30, v/v), presenting a purple color against a slightly colored background. This TLC system is quantitatively evaluated in terms of stability of the color, precision, accuracy, and calibration. Activation is performed at 110 degrees C. Stability of the color of both analytes is reached after 12 min. Precision, less than 5%, is obtained at two levels. Good linearity is obtained in the range of 0.5-8 micro g for all analytes. Some applications show its utility in the quality control of capsules. The prederivatization technique, applying the described dipping reagent before development, reveals the presence of various reaction products, possibly isomers. These results prove that TLC can be a cheap and easy alternative for the analysis of AT and its lipophilic derivatives, AM and AE, as pure powder and in pharmaceutical-dosage forms.