Late blight caused by Phytophthora infestans is one of the most destructive dis-eases potato in Egypt and world wide. Stability of resistance to late blight was eva-luated in twenty five potato cultivars during 2003 and 2004 successive seasons un-der heavy natural infection. Data showed that the potato cultivars Altesse, Occania, Safrane and Soleia highly resistant while cultivars Daisy, Hermine and Isabel rec-orded the highest susceptibility to late blight. Application different fungicide against potato late blight revealed that Aquagen Bro and Previcur-N were the best effective fungicides in reducing disease severity and progress of late blight. Data showed also that the losses of tubers due to late blight in season 2003 ranged from 11.75 Kg/plot (cultivar Hermes) to 18.0 Kg/plot (cultivar Lady Roseta) while in season 2004, yield losses ranged from 11.25 Kg/plot (cultivar Hermes) to 23.75 Kg/plot (cultivar Spun-ta). The results demonstrate that integration of Previcur-N treatment with host resis-tance was effective in reducing late blight and tuber yield loss of potato.