Intramolecular energy transfer occurs in the terbium complex with pipemidic acid (PPA) and the terbium(III) ion fluorescence can be sensitized by PPA. The fluorescence intensity of the Tb3+-PPA system is proportional to the amount of PPA. Accordingly, a fluorimetric method for the determination of PPA is proposed. The characteristics of the method include low background noise, high selectivity and long fluorescence lifetime. The method can be applied to the determination of PPA in urine and serum. The recovery is in the range of 94.6%-102%. Its detection limit and linear range for PPA are 3.6 ng/mL and 5.0 x 10(-8)-4.0 x 10(-6) mol/L, respectively.