Preparations sold as ecstasy pills (primarily 3,4-methylenedioxy-methamphetamine and its congeners) are increasingly being abused as a recreational drug in Europe. The production of these illicit pills involves three major steps: synthesis of the active compound, addition of excipients (e.g., adulterants, diluting agents, dyes, and lubricants), and compression of the pill. The analysis of dyes in pills may provide several kinds of information. Because of differences in laws, some food dyes allowed in the European Union are not allowed in Switzerland. Finding such a dye in pills suggests it is not locally produced. On the other hand, the dyes-based comparison between pills or between pills and dyes found in an illegal laboratory is useful information. The analytical process described has been developed for 14 hydrosoluble acidic, synthetic food dyes that are allowed in the European Community. The proposed analysis of dyes is based on three steps: extraction of the sample (30 mg) in acidic water and purification by thin-layer chromatography, either on silica gel or on cellulose (two complementary elution systems required), and confirmation of the identification and quantification by capillary zone electrophoresis coupled with a diode array detector. Two kinds of samples were measured. The first sample consisted of 10 pills that apparently belonged to the same batch. It was tested for qualitative and quantitative homogeneity. The second sample consisted of 43 pills that came from 43 different seizures; only qualitative analysis was done on this sample. Among the 43 colored pills, 40 contained dyes that belonged exclusively to the list of 14 food dyes allowed in the European Community. One contained a natural dye, and two contained dyes that could not be identified. The information derived from dye analysis can contribute to both tactical and strategic drug intelligence. Ways to use this information could be modeled through a quantitative evaluation that uses a continuous likelihood ratio assessment methodology. 5 figures, 4 tables, and 10 references