An ion chromatographic method is described for the determination of nicotine and cotinine in aqueous solutions. This method is based on a type of reversed-phase chromatography involving ion pair formation of protonated nicotine, cotinine, pyridine, and pyridine derivatives. Detection is accomplished by measuring the UV absorption at 262 nm. Detection limits for nicotine and cotinine are 8 ng/mL and 2 ng/mL, respectively. Analyses of environmental samples and spiked environmental samples by both this ion chromatographic method and a previously reported gas chromatographic method have been used to demonstrate the accuracy and precision of this technique. The results of the analyses of both sets of samples by the two methods are in excellent agreement with a linear correlation coefficient of 0.97.