Abstract: The aim of our work was to increase the explanatory power of field tests on the health of oilseed rape. We worked with sclerotia of the pathogen Sclerotinia sclerotiorum and conidiospores of Phoma lingam. Pathogen isolates were obtained by collecting tissues of infected plants and isolating the pathogen from infected tissue. Sclerotia were applied to the soil at concentration of 1.5 sclerotia per 1 m2 when sowing oilseed rape. Conidiospores were applied by foliar spray at concentration 20×109 per 1 ha in autumn and in spring. Monitoring was carried out on three varieties of winter oilseed rape with different resistance level to monitor the pathogens. Field trials were established in years 2011/2012 and 2012/2013 at two locations in the Czech Republic – in Opava and Šumperk. The results confirmed the effect of year, locations and infection pressure of pathogens. The tests revealed different reactions of the different varieties with respect to artificial inoculation. The experiments revealed different effects of the treatments. Whereas all varieties were more frequently diseased after inoculation with S. sclerotiorum, phoma inoculations displayed higher disease incidences only on cultivars Asgard and NK Morse but had no significant effect on cultivar Da Vinci.