Many kinds of plant diseases, insect pests and nematodes have frequently occurred on plants of crop fields, gardens and roadsides of Japan and caused damage to agricultural and horticultural crop fields, gardens plants and roadside trees. Plant disease and insect pest diagnosis, which are usually undertaken at agricultural experiment stations, plant protection offices and extension offices, are very important to food security, food production and keeping plants in the environment healthy. I have researched data bases on plant diagnosis of the Chiba Agricultural Experiment Station and Nara Prefectural Protection Office, and showed issues of plant diagnosis. I also prsent an outlook future plant clinical practices of Japan.