Ecology, mass production and release of a lady beetle, Coccinella septempunctata brucki, were investigated in Japan to use the beetle as a biological agent for controlling alfalfa aphids. In the alfalfa field, the number of overwintered aphids, Acyrthosiphon kondoi, increased on alfalfa in April and the occurrence from late April to mid-May showed a marked peak. Without C. septempunctata brucki, the reduction of alfalfa yield by aphids amounted to 40 to 70%. The overwintered adults of C. septempunctata brucki appeared in early March on the alfalfa field and began predation and oviposition. In total about 20% of the egg population developed to adults successfully. For mass production, A. pisum population was reared on Vicia faba as prey for the lady beetle. The overwintering adult lady beetle was used to obtain the eggs for mass production. The optimum development stages for release to the alfalfa fields where C. septempunctata brucki was absent were the 2nd, the 3rd and the 4th instar larvae in early March when the maximum temperature was around 10℃. The Japanese pampas grass, Miscanthus sinensis, was planted near the alfalfa field for keeping lady beetle populations in winter and summer as their overwintering and estivating sites.