A rapid and simple determination of acrinol (2-ethoxy-6, 9-diaminoacridine monolactate) in pharmaceutical preparations was investigated by FIA. The sample solution was injected into the carrier stream (water), merged with 0.5% potassium nitrite and 0.5% hydrochloric acid and then passed through a 10 m reaction coil (0.5 mm i.d.) at room temperature. Absorbance was measured at 517 nm. There was a linear relationship (r =0.999) between peak height and concentration of acrinol. The proposed method was successfully applied to the determination of pharmaceutical preparations.