A sequential injection spectrophotometric method for the assay of bromazepam anxiolytic drug has been reported. The method is based on the complexation reaction of bromazepam with iron(II) in hydrochloric acid media and spectrophotometrically measuring the product at lambda(max)=585 nm. A comprehensive chemometrical optimization treatment was successfully utilized for determining the proper optimum operating conditions for both the system and the chemical variables. The experimental design approach was employed and a 2(k) factorial design was run for studying the interaction effects of four factors namely, hydrochloric acid concentration, iron(II) concentration, delay time and flow rate. The super modified simplex algorithm was utilized for optimizing the three highly interacting factors which were, hydrochloric acid, iron(II), and delay time. The conditions obtained were 150 microl 0.110 mol l(-3) hydrochloric acid, 75 microl 0.328 mol l(-3) iron(II), 1200 s delay time and 40 microl s(-1) flow rate. The method was found to be suitable for the determination of Bromazepam in pharmaceutical preparations and the results obtained for the assay of the compound in proprietary drugs indicate that the method suffers no interference from excipients.