American wildrice (Zizania palustris) cultivars grown in Minnesota can be affected by stem rots caused by Nakataea sigmoidea (=Sclerotium oryzae) and Bipolaris oryzae. Genetic differences between cultivars have not previously been characterized. Likewise, neither heritability nor gain from selection have been estimated. Variety trials were inoculated with both of these fungal organisms to estimate broad-sense heritability for stem rot symptoms. Replicated half-sib families were inoculated and rated for stem rot severity. Heritability and gain from selected were estimated for both stem rot and foliar disease, and correlations between these and other traits were estimated. Alternative inoculation methods were compared for effectiveness in producing consistent results for severity ratings. Methods of evaluating stem rot severity are compared and discussed. Since Sclerotium oryzae also causes stem rot in rice (Oryza sativa), methods of inoculating and evaluating stem rot in wildrice may have applicability to rice.