To assess actual foliage damage due to potato leaf miner, Liriomyza huidobrensis (Blanchard), commercial potato pockets of Lalitpur, Kathmandu, Bhaktapur, Kavrepalanchwok, Sindhupalchwok and Makwanpur districts of Mid-Nepal were surveyed in 2009. Percent foliage damage analysis and ANOVA (with unbalanced frequency distribution) of multiple regressions of different factors were done to evaluate the level of damage and factors significantly influencing damage. Damage level was found more in lower altitudes (790-1568 meters above sea level) than in higher altitudes (1560-2610 meters above sea level). Similarly, lower leaves were more damaged than the upper ones. So, altitude and plant age were two factors influencing damage by test insect. Since the pest is becoming severe and can withstand chemical sprays, it is imperative to develop suitable IPM technique against this insect. Similarly, strict quarantine and awareness campaign against this insect pest are crucial to check its migration to virgin potato pockets.