The formation of tobacco specific nitrosamines (TSNAs) in various tobaccos has become a topic of importance in recent years. The significant formation of TSNAs in burley tobacco occurs after the yellowing phase of curing and is dependent on several factors, notably the fertility level during growth and the curing environment during the browning and drying phase. Several field curing studies at the University of Kentucky Agricultural Experimental Station have focused on the relationships of curing environment and the resulting TSNAs of lamina and midrib components. The environmental treatments have included whole plant harvest and natural air curing in a barn and field curing structures, field curing structure with supplemental fan circulation and laboratory chamber curing of 'bulk' leaves in an accelerated eight to ten day schedule. Results show TSNA levels ranging from under 1 ppm up to 20 ppm for the various treatments. Generally, the lower levels of TSNA have resulted from curing in a more rapid drying regime than normal with the resultant leaf quality not as desirable to the buying representatives. Studies are continuing on a combination of cultural practices and curing environments that will produce desirable burley qualityand the lowest possible TSNA levels.