Brown patch, caused by the fungus Rhizoctonia solani Kuhn, is one of the most devastating diseases that can occur on Tall fescue (Festuca arundinacea Schreb.). Currently, the most effective control option to reduce disease severity is through the application of costly fungicides.  The development of resistant cultivars to brown patch would greatly reduce the need for fungicide applications, however the genetic mechanism of brown patch resistance is not known in tall fescue.  The objectives of this study were to: (i) determine narrow-sense heritability and gain from the selection and (ii) calculate the number of effective loci involved in brown patch resistance.  In 2006 reciprocal crosses were made between 3 resistant and 3 susceptible genotypes using a diallel design.  100 seedlings from each reciprocal cross were randomly selected and planted in a field trial in the fall of 2006 along with clonal replicates of each of the parents.  The field trial was arranged in a randomized complete block design with four replicates with twenty five progeny from each reciprocal cross representing each replication.  Plots were maintained as mowed spaced-plants at a height of 5.08cm.  To ensure uniform disease pressure, the field was inoculated with a single R. solani isolate at a rate of 0.6 g m^-2 of prepared inoculum. Visual disease ratings were taken on a weekly basis when symptoms of the disease appeared using a scale of 1-9, with 9 representing the least amount of disease.  Preliminary analysis indicates a narrow-sense heritability of 0.81.