Abstract: A mathematical treatment for the determination of equivalent points in potentiometric acid-base titration is presented. The detection of end point of titration by means of linear graphic method and calculation method is recommended. Weakly acidic drugs with stability constants ranging from 10⁷¹0¹⁰ have been titrated. Some weakly acidic water-soluble drugs (nicotinic acid, boric acid, fluorouracil, pilocarpine nitrate) have been determined. This method is simple and convenient to operate. The accuracy and precision meet the requirements. Monte Carlo method has been employed to study the effect of error in pH data on the results.