Capillary electrophoresis (CE) describes a family of related techniques in which separations are conducted in narrow bore capillaries under the influence of an electric field. The separations obtained are highly efficient and quick and may be applied to both charged and neutral species. The analysis of heroin and associated opiates in drug seizure samples is important in forensic investigations. Micellar electrokinetic chromatography (MEKC) is one mode of CE that has been applied to the analysis of opiates in heroin seizure samples. In the procedure described in this paper, separations were performed with the use of an uncoated fused silica capillary, 50 cm x 50 um I.S. x 360 um O.D. with an effective separation length of 8 cm. The system was run at 25 degrees C with an applied negative voltage of -25 kilovolts. Injection of each sample was for 2 seconds at -50 mbar. Ultra-violet detection was used with the wave length set at 210 nm. The background electrolyte consisted of 85:15 (water:acetonitrile, v/v) containing final concentrations of 25 mM SDS and 15 mM sodium borate, pH 9.5. Samples and standards were prepared in 0.1 percent v/v acetic acid and diluted in the run buffer that contained 1 mg/ml of N,N-dimethyl-5-methoxytryptamine as an internal standard. Under these conditions, a text mixture that contained caffeine, paracetamol, morphine, codeine, heroin, and acetylcodeine was resolved within 1.5 minutes. The method was used to determine the concentration of heroin in seizure samples, and the results were similar to those obtained by a validated gas chromatographic method. 7 tables, 3 figures, and 38 references