A new bacterial disease has been observed on crucifers in Shizuoka, Aichi and Nagano Prefectures, Japan, since 1983. The disease appeared on the leaves as pin-point, watersoaked lesions which enlarged to form gray, necrotic spots. The causal bacterium was a gram negative, aerobic rod with single polar flagellum. It formed yellow slimy colonies, liquefied gelatin, produced hydrogen sulfide and hydrolized starch. It neither reduced nitrate to nitrite, nor produced arginine dihydrolase. The bacterium produced acid in the media added glucose, sucrose, lactose, starch, mannitol and dextrin, but not in those added ribose and dulcitol. On inoculation, the bacterium showed strong pathogenicity not only on several crucifers, with formation of numerous spots similar to natural infection, but also on tomato, physalis plant, cucumber and pumpkin. From these results, the causal bacterium was identified as Xanthomonas campestris pv. raphani (White 1930) Dye 1978. This is the first report of bacterial spot disease of crucifers in Japan.