A sensitive and fast chemiluminescence (CL) flow-injection method has been described for the direct determination of carbaryl. The method is based on the enhancing effect of carbaryl on the CL emission generated by the oxidation of luminol with potassium permanganate in an alkaline medium. The optimisation of instrumental and chemical variables influencing the CL response of the method has been carried out by applying experimental design, using the proposed flow-injection manifold. Under the optimal conditions, the CL intensity was linear for a carbaryl concentration over the range of 5–100 ng ml−1 with a 3σ detection limit of 4.9 ng ml−1. The method has been successfully applied to the determination of carbaryl residues in water and cucumber samples.