Pollution of the environment with radionuclides and heavy metals has become a serious global problem. Therefore, the study on the uptake of trace elements by plants is urgent for the risk assessment. The uptake of various elements by plants was simultaneously traced by the multitracer technique that was developed by the RIKEN group. The multitracer consists of radionuclides of not only essential elements but also harmful elements. The multitracer technique enables us to obtain information on the behavior of various elements under the strictly identical conditions. The first application of the multitracer technique was the study on the uptake of trace elements by rice and soybean plants grown in culture solutions. The multitracer study was focused on the following subjects: Foliar uptake of trace elements by soybean, Japanese radish, and mung bean plants and determination of their mobility: The effects of soil acidity and Al concentration on the uptake of various trace elements by soybean, tomato, and carrot plants: Binding affinity of trace elements to an apoplast protein of soybean root in the presence of Al: Ion competition effects on the absorption of trace elements in komatsuna and carrot: Transfer factors of radionuclides for soybean, komatsuna, and mushrooms: Subcellular distribution of radionuclides in the leaves of soybean, cucumber, and autumn fern: Effects of microorganisms on the uptake of trace elements by rice, tomato, cucumber, marigold, and ryegrass: Screening of plant species for phyto-remedaition of soil contaminated with radionuclides. The results obtained provided valuable information to ecology, plant physiology, and nutrition.