The FDA Center for Tobacco Products (CTP) has identified ammonia as a harmful or potentially harmful constituent (HPHC) in tobacco and tobacco products. However, there is currently not a single generally accepted method for the determination of ammonia in mainstream tobacco smoke. Several analytical techniques are commonly used to measure ammonia, including Ion Chromatography (IC) with a conductivity detector, LC-MS/MS and spectrophotometric detection. For this study, two methods were used, ion chromatography and spectrophotometric detection. We will present the ammonia concentration determined in each method in the mainstream smoke from 3R4F, CM7 and 1R5F reference cigarettes under both ISO and Canadian Intense smoking regimes. The results for each method will be compared along with the advantages and disadvantages of each analytical technique.