ABSTRACTCurrent literature indicates conflicting results as to the relative stability of thiamin mononitrate versus thiamin hydrochloride. These salts were tested for stability at 75–95°C and at aw's 0.58 and 0.86. The observed difference in stability of the two salts can be explained by the higher activation energy (26.3 vs 22.4) for the mononitrate which results in a crossover point at about 95°C in an Arrhenius plot. Below 95°C the mononitrate was more stable while above 95°C the hydrochloride is more stable. In addition, stability of both forms was slightly less at the higher aw. The loss of thiamin mononitrate in a fluctuating square wave temperature could be accurately predicted using the results of the Arrhenius