Differences in TSNA accumulation between burley genotypes can often be attributed to differences in nicotine conversion and/or differences in amount of total alkaloids. However, several researchers have observed differences in TSNAs between certain cultivars that cannot be explained by either of these factors. KT 204LC tends to have lower TSNAs than NCBH 129LC, especially under curing conditions favorable for TSNA accumulation. In a two-year study, these two cultivars were sampled throughout curing, and TSNAs, alkaloids, nitrogenous constituents and leaf surface chemicals were measured. NCBH 129LC had higher TSNAs and higher nitrite nitrogen than KT 204LC throughout the cure. The nitrite nitrogen in KT 204LC increased very little in either lamina or midrib, but the NCBH 129LC nitrite nitrogen increased rapidly from 20 days after harvest. Nitrate nitrogen was higher in NCBH 129LC. Conversion, nornicotine, total nitrogen and total alkaloids were higher in KT 204LC. KT 204LC would therefore be expected to have higher TSNAs, but it did not. Duvatriene diols were also higher in KT 204LC throughout the cure, contrary to our working hypothesis. It is likely that the lower TSNAs observed in KT 204LC are due largely to the lower nitrate to nitrite reduction in that cultivar.