Tobacco specific nitrosamines (TSNA) in burley tobacco are formed during air-curing in the reaction of alkaloids, such as nicotine and nornicotine, with nitrite nitrogen. Nitrite in leaves is formed by the reduction of nitrate by microorganisms mainly in the browning and stem drying phases. The formation of TSNA in the stem-drying phase is greater than that in other phases, because this phase has a longer time compared to other phases. To shorten the stem-drying phase, burley leaves were cured in the same curing environment as flue-cured tobacco in a bulk curing barn. The rapid increase of TSNA without any nitrite increase was observed in the stem-drying phase (temperature of the stem-drying phase: 68 °C). To study the temperature of the stem-drying phase enough to suppress the formation of TSNA, leaves at the end of yellowing and at the end of browning were cured at constant temperatures of 40, 50 and 60 °C until the stems were completely dried. The TSNA content in the lamina cured at 50 °C was lower than that at other temperatures. A rapid increase of TSNA was observed at 60 °C although the curing period was shortest. The formation of TSNA in the lamina cured at 40 °C was not suppressed because the stem-drying period was longest compared to other temperatures. Furthermore, we examined in a bulk curing barn the stem-drying conditions of air flow and air ventilation that would reduce the formation of TSNA in burley cured leaves. The TSNA contents in the lamina and stem cured at a constant temperature of 50 °C, with high air flow and with continuous air ventilation, were much lower than those conventionally cured.