Abstract: A sensitive, simple and inexpensive chemiluminescence (CL) method using flow injection is described for the determination of two β-lactamase inhibitors sulbactam sodium and clavulanic acid (potassium salt) in their pure form, in pharmaceutical preparations and added to blood serum. The method is based on the enhancing effect of these compounds on the CL generated by the oxidation of luminol with hydrogen peroxide in alkaline medium. The CL intensity is a linear function of sulbactam sodium concentration over the range 0.1-150 µg mL-1 with a detection limit (2 x noise) of 0.05 µg mL-1, and for clavulanic acid over the range 0.01-12 µg mL-1 with a detection limit of 0.01 µg mL-1. The method is applied successfully to the determination of the drugs in their dosage forms without interference from co-formulated drugs. The method is specific for the intact drugs in the presence of their degradation products.