Several experiments were conducted in 1997 and 1998 at the Bergerac Tobacco Institute to investigate the effets of variety, nitrogen fertilization and after-curing storage modes on TSNA concentrations in air-cured tobaccos, Burley and dark types. The comparison of such tobaccos confirmed that, for both types, TSNA concentrations (1,4-3,8 ppm) were positively linked to total alcaloid concentration. In particular, concentrations of NNN, the predominant nitrosamine (0,5-2,5 ppm), were closely linked to nornicotine concentration in cured leaves, whereas NAT concentrations (0,3-1,2 ppm) were linked to anatabine concentration. Increasing nitrogen fertilization on dark tobacco from 250 to 500 units. ha^-1resulted in an increase of around 50% in TSNA concentrations. Several modes of storage, differing in duration, temperature and tobacco moisture concentration, were applied to dark tobacco. TSNA concentrations increased with time, more or less markedly, for all storage modes.The highest TSNA concentrations (9-13 ppm) were observed after leaf storage at a high moisture content (28%), during a long period of time (6 months).The results of these studies show that TSNA concentrations in air-cured tobaccos can be controlled by actions at the following levels:- breeding (total alcaloid concentration and frequency of nicotine-nornicotine conversion);- cultural practice (nitrogen fertilization);- post-harvest treatments.