Northwestern Pakistan is the leading seed potato-producing area of the country. Potato cultivars grown commercially in the region were screened against Potato mop-top virus (PMTV) under screenhouse conditions and in naturally infested fields during 2010-2014. The potato cultivars, Asterix, Cardinal, Desiree, Diamant, Kuroda, Paramount, Raja, Rocco, Sarpomira, and Ultimas, were grown in viruliferous soil in a bait test and were all found to be susceptible to PMTV (two isolates from Pakistan-Hazara (PMTV-PkH) and Pakistan-Malakand (PMTV-PkM)) in screenhouse experiments. The virus was detected in all cultivars as tested by double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) in leaf, root, and tuber samples, and by back inoculation of sap from roots of bait plants on indicator plants. The ELISA values (A(405nm)) were lower in leaf, root, and tuber samples in cultivar Desiree compared to the other cultivars, whereas in the infectivity assay, the virus was recovered in all cultivars and exhibited characteristic symptoms on diagnostic hosts. All 10 potato cultivars were further tested against PMTV in previously known infested fields at Baffa, Hazara division, and Kalam, Malakand division, in northwestern Pakistan. The cultivars tested at both sites were found susceptible to PMTV. The virus was detected by DAS-ELISA and RT-PCR in randomly selected potato tubers of each cultivar during 3 years at both sites. We conclude that commercially grown potato cultivars in northwestern Pakistan are susceptible (moderately sensitive to sensitive) to PMTV, requiring a comprehensive potato germplasm screening program for the evaluation of sources of resistance against the virus.