The population densities of Cabbage aphid Brevicoryne brassicae (L.) were studied on the thirteen varieties of rapeseed mustard crop. The aphid population were found from February to May, and peaked in the last week of March. The greater aphid densities were recorded on leaves and flowers as compared to stems. The significantly higher aphid populations was recorded on CON-I variety as compared to others rapeseed mustard varieties. The lowest significant numbers observed on KS 74 variety.