Technical Abstract: Peas (Pisum sativum L.) are subject to a number of bacterial, fungal, viral, and nematode diseases, which can significantly decrease both yield and quality. Soilborne fungal diseases discussed in this chapter include seedling diseases caused by Pythium spp. and Rhizoctonia solani; root rots caused by Aphanomyces euteiches and Fusarium solani f. sp. pisi; and wilts caused by Fusarium oxysporum f. sp. pisi races 1, 2, 5, and 6. Also discussed is the problem caused by pea cyst nematode. Foliar diseases caused by fungal pathogens include white mold caused by Sclerotinia sclerotiorum, powdery mildew caused by Erysiphe pisi, downy mildew caused by Peronospora pisi, Ascochyta blight caused by Ascochyta pisi, Mycosphaerella pinodes, and/or Phoma medicaginis var. pinodella. Peas are subject to an array of bacterial, fungal, nematode, and viral diseases which affect the foliage and/or roots. Many of these diseases can be readily controlled by growing resistant varieties. Such diseases as bacterial blight, downy mildew, powdery mildew, and fusarium wilt are examples. Also, many viral diseases such as pea seedborne mosaic, bean leaf roll, and pea enation that cause serious diseases in peas are also controlled by growing resistant varieties,. What is encouraging is that resistance to most of these diseases has been relatively stable over the years. The notable exceptions are bacterial blight and downy mildew where new races/strains of the pathogen keep appearing. In this chapter, we have attempted to describe the most important diseases of peas on a national and international scale, the disease symptoms, the pathogen, and give the currently acceptable control practices.