The research was carried out in field conditions in Bonin in the north of Poland, in 1996–2009, and additionally in Bonin, Przechlewo (also in the north of Poland) and Stare Olesno located in the southern part of Poland, in 2008 and 2009. The outcome showed that Potato virus Y posed the most serious threat to potatoes. The share of progeny tubers infected by this pathogen was 32.5% (mean of 1996–2009) and was considerably higher in comparison to PVM (18.2%) and PVS (22.1%), and in particular to PLRV (15.3%). The additional research carried out in the years 2008 and 2009 in three places: Bonin, Przechlewo (located in the north of Poland) and Stare Olesno (south of Poland) included three potato cultivars of low resistance to PLRV. The results also showed a very low pressure of this virus in both years and in all places of the research. In Przechlewo, PLRV was not detected at all in progeny tubers. While in Stare Olesno and particularly in Bonin, the percentage of PLRV-infected tubers was very small. The average for years and the average for localities amounted to 2.1 and 0.3%, respectively. Whereas the share of tubers infected by PVY, PVM and PVS was considerably higher and ranged from 11.8% to 59.8% depending on the cultivar, year and place. The progeny tubers infected by PVY and PVM were mostly detected in the very early term of exposure(from the 21st of May to the 1st of June). Whereas PVS posed the most serious threat in a somewhat later term i.e. during the exposure of plants which lasted from the 1st of June to 11th of June