As vegetables are often grown under continuous cropping in Japan, injury associated with continuous cropping is frequently observed. Although the methods of control are based on the use of chemicals, the importance of promoting sustainable cultivation and environment-friendly technologies is being increasingly recognized. Plant diseases caused by fungi or bacteria, such as clubroot, yellows are major problems. To address these problems, crop rotation with sweet corn, introduction of resistant radish varieties as trap crops or inoculation with endophytes have been applied. Injury caused by nematodes is also a serious problem. Practical methods using antagonistic plants such as marigold have been developed, because only one season is required to introduce these plants with only minor changes in the cropping systems. Selection of crop combinations is essential. Taro (Colocasia esculenta Schott.) is severely damaged by a root lesion nematode (Pratylenchus coffeae). By examining the degree of suppression of this nematode by many kinds of crops, determination of crop sequence efficiency became possible for the control of nematodes and offers a wider range of selection of crop combinations. Taro is injured by P. coffeae and by the root knot nematode (Meloidogyne incognita), while radish (Raphanus sativus L.) is attacked by the root lesion nematode (Pratylenchus penetrans). The combination of these 2 vegetable crops with a third one, such as vegetable soybean (Glycine max), can minimize the injury caused by these 3 nematodes.