Pyrenophora teres f. teres is a fungal pathogen that causes barley net form net blotch. To evaluate the genetics of resistance in barley, a RIL population was developed using resistant barley lines CI5791 and Tifang and tested against a global collection of nine P. teres f. teres isolates. QTL analysis indicated that CI5791 resistance mapped to chromosome 6H and was effective against all isolates. Additionally, CI5791 harbored resistance on chromosome 3H effective against two Japanese isolates. Tifang also had resistance that mapped to 3H and was effective against four of the isolates. To evaluate the genetics of virulence in P. teres f. teres, a fungal population was developed and evaluated against ten barley lines. 19 unique QTL were identified on 12 different linkage groups. 1 or 2 major loci were identified for a few of the barley lines whereas for most lines, virulence was contributed by several loci.