Background: Late Blight Disease, caused by the fungal pathogen, Phytophthora infestans, is a major constraint of Irish potato production in Kenya. The disease can destroy a crop, causing up to 100% yield loss. Small scale holder farmers in Kisii County continuously grow Irish potato that is susceptible to P. infestans, which require a number of fungicide sprays. This study was formulated out of the realization that Irish potato plays a major role in food security and contributes to poverty alleviation. Also, the commonly used protectant fungicides for late blight disease are expensive, hazardous and are not effective against P. infestans . Aim: To evaluate the effect of host resistance to foliar late blight severity, disease development and progress on selected potato varieties under field and glasshouse conditions in Kisii County, Kenya. Study Design: Nine potato varieties (Tigoni, Meru red, Kenya mpya, Sherekea, Shangi, Purple gold, Asante, Mang’ere and Nyayo) were grown in the field and glasshouse following a randomized