Although tobacco is an agricultural crop, little has been published on the variability in NNN levels in tobacco grown within a single crop year (intra-crop year variability) by multiple growers. Furthermore, the potential impact of intra-crop year variability of NNN levels in tobacco on NNN levels in smokeless tobacco products is unknown. In this work, NNN levels were measured in dark air-cured, dark fire-cured and Burley tobaccos used to produce smokeless tobacco products over either a six or ten year crop period. Additionally, NNN levels were measured in nine smokeless tobacco products manufactured over seven years. Only results from smokeless tobacco products manufactured using a single crop year of tobacco were included. NNN measurements over ten crop years for dark air-cured and dark fire-cured tobacco and over six years for Burley tobacco demonstrated a 10-fold range (lowest concentration to highest concentration) within a single crop year. Mean NNN levels exceeded 1 ppm in dark fire-cured and Burley tobacco in every year tested and six of ten years for dark air-cured tobacco. Depending on the specific smokeless tobacco product and year, the measured NNN levels generally varied from three to six fold within a single crop year. Over the seven years, NNN levels exceed 1 ppm (dry weight basis) for the vast majority of smokeless tobacco product measurements. The demonstrated variability in measured levels of NNN in smokeless tobacco products, due to natural variability in levels of NNN in tobacco, provides significant insight about measured NNN levels among smokeless tobacco products.