A simple method is presented for the determination of atenolol in tablets. The method is based on the formation of an ion-pair between atenolol and bromothymol blue (BTB) in pH 5.8 aqueous solution. The ion-pair was extracted into chloroform and the aosorbance of the chloroform layer was measured at 414 nm against a blank solution. A linear relationship existed between absorbance and atenolol concentration over the 2.5 - 15.0 μg. ml-1 range. The molar ratio of atenolol - BTB was determined as 1:1. The stability constant of the ion-pair was calculated (logK= 6.39). Using the present method commercially available atenolol tablets were assayed. The results were statistically compared with those obtained by UV-spectrophotometric method by t- and F- tests at 95% confidence level. Calculated t and F values were both lower than the tabulated values. Keywords :