The presence of succinylacetone in urine or blood or amniotic fluid is pathognomonic of an inherited metabolic disorder, named tyrosinemia type I. We developed a capillary electrophoretic method for the fast analysis of succinylacetone in urine samples. The separation was performed at reversed polarity mode using either a cationic surfactant as the buffer additive, or a capillary coated with a positively charged polyelectrolyte. Under these conditions, urine samples were directly injected to the capillary without any pretreatment step. The utility of the method was demonstrated by the identification of succinyacetone in urine from patients with hereditary tyrosinemia type I. For all patients, diagnostic peaks at the expected migration times were detected. The developed method is rapid, simple, inexpensive, and suitable for the determination of succinylacetone in clinical urine samples. (c) 2005 Elsevier B.V. All rights reserved.