The electrochemical oxidation of a synthetic wastewater containing Acid Yellow 1 on boron-doped diamond was investigated. The influence of applied current (0.5-3 A), dye concentration (1-3 g L-1), temperature (25-40 degrees C) and flow-rate (75-300 L h(-1)) on colour removal and current efficiency was evaluated. It was demonstrated that the complete decolourization and COD removal were achieved in any experimental conditions indicating that the electrochemical oxidation on BDD electrodes is a suitable method for treatment of wastewaters polluted with synthetic dyes. In particular it was found that the decay of Acid Yellow 1 follows a pseudo-first-order kinetic and the oxidation rate was favoured by increasing current and flow-rate, while it was almost unaffected by solution temperature.