PVY was mentioned for the first time in Iran in an internal survey of 1968-69, reporting outbreaks on a field of Virginia Hicks as well as fields of Guilan tobacco at the Research Institute of Tirtash. During the last ten years, PVY has been frequently observed on cv. Guilan whereas outbreaks remained negligible in the Mazandaran region, and often masked by infestations from TMV and CMV; however, in 1994-95 and in 1997, outbreaks of PVY on a few cvs. of Coker 347 in the regions of Gorog and Fazel-Abade were a clear signal of an emerging problem. In order to better assess the presence of PVY and the performance of various cultivars against this virus, the Institute has participated since 1996 in the CORESTA collaborative trial and grown the trap collection. Results are as follows: the climate of 1996 was not conducive to virus diseases and no virus symptom was observed, even on sensitive varieties of the CORESTA trap collection. However, in 1997 conditions were very conducive to appearance and propagation of virus diseases (mainly due to TMV and CMV) and, in some places, they caused extensive damage on cv. Virginia. There was little damage at the Institute. In the collaborative trial, some mosaic and necroses specific of PVY were observed. The varietal difference is significant at the threshold of 1%. 1) For mosaics, Virg. SCR, TN86 and VAM were the most resistant whereas K 326, Burley 21 and Coker 347 were the most sensitive. 2) For necroses, MN 944, Virg. SCR were the most resistant and VAM, Tirtache 30 and K326 were the most sensitive. 3) For both symptoms (mosaic and necroses), Virg. SCR, TN 86, MN 944 were the most resistant and K 326, Burley 21, Tirtache 30 and Coker 347 the most sensitive.