Tobacco specific N-nitrosamine (TSNA) formation increases in tobacco leaf after the hydrolytic stage of curing, usually visualized as the end-of-yellowing. The oxidative reactions follow the yellowing stage and it is during the oxidative stage and before the leaf becomes air-dry that TSNAs accumulate. As membranes become leaky the cell compartmentalization breaks down and cell contents mix within the cell as well as become available for chemical and exogenous biotic reactions. These reactions include microbial reduction of nitrate to nitrite and nitrosation of the alkaloids to form TSNA. Therefore, if moisture loss is rapid and complete soon after end-of-yellowing, accumulation of TSNA is minimized. The objective of the present study was to evaluate diverse tobacco lines for differences in leaf thickness, specific leaf weight, methylene chloride soluble leaf surface substances and rate of water loss with TSNA accumulation. Tobacco lines cured were burley tobaccos TN 90, a secreting type, and KY 8538, a non-secreting type; McNair 944, a flue-cured tobacco; and dark air-cured tobaccos Galpao, KY 171, KY 160 and a near isogenic Pale Yellow Low Nicotine KY 160 (PYLN KY 160). Water loss from tobacco was determined at weekly intervals. Methylene chloride soluble substances were determined from the green leaf at harvest. Thickness and specific leaf weight was determined on green and cured leaf. TSNA, alkaloid and nitrite analyses were done on cured leaf. Leaf thickness and specific leaf weight was greatest in the dark tobaccos and least in burley tobaccos. Methylene chloride solubles were generally greatest on the dark tobaccos. Water loss was not significantly correlated with leaf thickness, specific leaf weight or methylene chloride solubles on the leaf. Water activity was very similar for all lines by four weeks of air-curing. In 1999, a dry curing season, nitrite and TSNA levels were low.