Spectrophotometric and spectrofluorimetric methods for the determination of five Angiotensin II type 1 receptor antagonists in tablets and plasma have been developed and optimized. The spectrophotometric method involves the addition of a measured excess of bromate-bromide in HCl medium and subsequent estimation of the residual bromine by reacting with a fixed amount of methyl orange. The spectrofluorimetric method depends on the oxidation of the drugs with cerium(IV) and subsequent monitoring of the fluorescence of the induced cerium(III) at 365 nm with excitation at 255 nm. Both of the proposed methods were successfully applied to the determination of the investigated drugs in their pure forms and pharmaceutical preparations. Besides, the spectrofluorimetric method was applied to the determination of irbesartan and telmisartan in biological fluids with good accuracy and precision.