A synthesis based on observations accumulated since the start of this collaborative work, which involved 145 trials in 26 countries between 1996 and 2002, will highlight the following results: - assessment of different PVY resistance sources, with regard to the global frequency of breakage of these resistances;- world distribution, frequency and trends of the tobacco disease caused by necrotic PVY strains. These results will be discussed by referring to knowledge concerning the PVY disease, namely: - consequences of the PVY disease on the tobacco leaf chemical equilibrium, - understanding of the resistance mechanism conferred by the "va" gene, - possibilities of control through breeding, - other possibilities of control. Application of this knowledge in the view of GAP programs will be considered, and new trends of the collaborative experiment will be presented.