A two-year experiment was done to study the pattern of accumulation of benzo [a] pyrene (B[a]P) and tobacco specific nitrosamines (TSNAs) during fire-curing, and to establish whether B[a]P and TSNAs can be reduced by modifying the firing regime. The 2012 study was done in a traditional fire-curing barn, with five firings, over a total of 25 days. B[a] P at takedown was 262 ppb, and total TSNAs were 5.4 ppm. The study was repeated in 2015, in a new, “tighter” barn, in which it is possible to achieve a satisfactory finish with fewer and shorter firings; a regime which might be expected to result in lower TSNAs and B[a]P. There were three firings, over a total of 18 days. B[a]P at takedown was 489 ppb, and total TSNAs were 8.5 ppm; much higher than in the 2012 study cured in the older barn with more firings. These results were unexpected, because the decrease in firing in the 2015 study would be expected to result in lower (B[a]P) and TSNAs. Seasonal differences can have a considerable effect on TSNA levels, but are unlikely to affect B[a]P levels. We are investigating possible causes of these anomalous results.