Streak resistant maize inbred lines released by the Grain Crops Institute in 1995 were evaluated in the absence of streak disease as hybrid combinations in field trials. The evaluation of single crosses between three lines in each of a B73 and Mo17 background identified one line which transfers resistance to northern leaf blight (Exserohilum turcicum) in all combinations. Modified single crosses of the same lines using I137TN as tester yielded significantly less than a commercial standard hybrid. In three-way hybrid combinations of B73 related lines crossed to MSV-resistant germplasm in seven other genetic backgrounds, and using I137TN as tester, several hybrids yielded equivalent to a commercial standard. Significant differences in the incidence of ear rot (Stenocarpella maydis) were observed. The results comfirm that MSV-resistant breeding material derived from the improved Vaalharts composite are competitive with commercially proven susceptible varieties.