Northern leaf blight is a lethal foliar disease of maize caused by the fungus Exserohilum turcicum. The aim of this study was to elucidate the pathogenic variability and Severity assessment of the fungus in maize. For pathogenic variability, spore suspensions of fourteen E. turcicum isolates of Meghalaya were inoculated in maize (Variety: Yellow local) at 3-4 leaf stages by means of an atomizer. Results showed that the maximum per cent disease intensity (42.23), virulence index (9.753), lesion length (9.31 x 0.74) and shortest incubation period (4.33 days) was observed in isolate RBEt 02 from Umsning, District Ri- Bhoi, followed by EJEt 03 from Saipong, District East Jaintia hills. The isolate EKEt 02 from Mawrynkhneng, district East Khasi hills showed minimum PDI (21.02), virulence index (2.744) and longest incubation period of 7.66 days. The virulent i.e RBEt 02 was further studied for the infection strategy. The leaves of inoculated plants and un-innoculated (control) were used for the study. Samples were prepared according to standard microscopy procedures and analysed using light microscopy as well as scanning electron microscopy (SEM). Conidia size was observed in the range of 13.2 and 134 μm length. The appressoria exhibited widths of 15-23 μm. Notably, the penetration of the leaf's epidermis occurred directly and specifically at the points where the epidermal cell walls met. Interestingly, penetration was not observed to occur through the stomata (tiny openings on leaf surfaces) or leaf trichomes (fine hair-like structures), even when in close proximity to these structure. The present study provide information about the virulence of Ri-bhoi district isolate as well as its infection strategy.