Fifty potato cultivars were screened for potato aphid, Macrosiphum euphorbiae Thomas infestation degree in the field. Aphid honey dew secretion and contents of foliar substances (glycoalkaloids, total nitrogen, Ca, K and Mg) of the cultivars were measured in the laboratory to analyze the correlation between infestation degrees and those factors. The number of aphids ranged from 4.1 to 31.4 per five leaves. The lower density (less than 5 aphids) was found on cvs. Jidose, Recent, and Sebago. The aphid secreted highest (40.3 droplets) and lowest (15.7 droplets) honeydew on cvs. Jopoong and Anco, respectively. Degree of infestation is positively correlated to glycoalkaloids and total nitrogen contents of the potato leaf.