Excessive amounts of nitrogenous fertilisers applied to dark air-cured tobacco are likely to increase the levels of non-reduced nitrogen in the tobacco. Non-reduced nitrogen will, under certain conditions, contribute to the formation of nitrosamines. A trial was consequently conducted with six levels of nitrogen, ranging from 350 to 500kg N ha^-1 in the Limpopo Province of South Africa. Increased levels of nitrogen had no significant effect on the yield, price or income. Under such lucratively fertilised conditions, the concentration of non-reduced nitrogen in the midrib of top leaves at harvest time was 2.6 times higher than that in the lamina. Data obtained after barn drying showed the highest concentration of non-reduced nitrogen (1.23%) together with the lowest concentration of TSNAs (0.77 mg kg^-1) in the lower leaves, and the lowest concentration of non-reduced nitrogen (0.68%) together with the highest concentration of TSNA_s (1.63 mg kg^-1) in the upper leaves. Data obtained after fermentation showed concentrations of non-reduced nitrogen very similar to those found after barn drying. The concentration of TSNAs in the lower, middle and upper leaves had increased to 3.78, 3.40 and 3.91 mg kg^-1 respectively (much higher than the values of 0.77, 1.10 and 1.63 mg kg^-1 obtained after barn drying). These data showed that TSNAs were mostly synthesised during fermentation and that the concentration of TSNAs had increased dramatically between barn drying and fermentation. Continued research directed towards the compilation of a fertiliser guideline for nitrogen is required.