Studies on Phytophthora-induced diseases of citrus depend upon several factors as the use of healthy and vigorous test plants, the activity of the pathogen, environmental conditions which favor the optimum disease development and expression and the availability of good inoculation and evaluation methods. In this work, it is described inoculation and evaluation methods that are used to study these diseases both in seedlings and in mature trees in orchards, with special emphasis on those that are used to study of Phytophthora gummosis and root rot of young plants.