Abstract: The relative performance of different inoculation methods viz., foliar spray, agarose gel method, soil application and seed treatment with Alternaria brassicae and Alternaria brassicicola was evaluated to standardize the methods of inoculation for screening. For A. brassicae two cultivars of Indian mustard namely Pusa Bold and Rohini were used to evaluate relative performance of inoculation methods, whereas for A. brassicicola the cultivars BS-2 and Kranti were tested. The foliar spray was found to be the most effective method of inoculation to achieve severe disease symptoms. Phylloplane population of the fungi was also recorded greater on the plants sprayed with spore suspension of Alternaria spp. The next in effectiveness in causing the disease and its further development was agarose gel inoculation. The plant length was decreased significantly due to inoculation with A. brassicae or A. brassicicola by foliar spray. Seed and soil inoculation methods resulted to mild blight symptoms but significant reduction in plant growth variables did not occurs. The regression analysis between the disease severity and yield decline has shown stronger relationship between the two variables for foliar inoculation followed by agarose gel method. The foliar inoculation caused the blight of severity that led to the yield decline greater than other methods. The study has demonstrated the spray of foliage with spore suspension of A. brassicae or A. brassicicola is highly effective method of inoculation.