Disease resistance to brown-spot needle blight of 7 geographic seed sources of slash pine and 10 of loblolly pine from USA was tested by planting 1~2 years old seedlings of these seed sources nearby a slash pine plantation which had been destroyed by brown-spot disease. The results showed that all the seed sources tested are highly susceptible to the disease although there are certain differences among them. 1~2 years old seedlings of 8 seed sources of slash pine from several provinces in south China were tested by artificial inoculation with brown-spot fungus in nursery and the same result was obtained. The parent slash pine stands of these seed sources were established in 1930s and 1940s respectively with exotic seeds. In severely infected slash pine plantations, slightly infected or non-infected individual trees are commonly detected. These resistant phenotypes are probably due to inheritence. In 1982, 47 brown-spot disease resistant slash pine trees were selected from Fujian and propagated by grafting on stocks of 4-years old slash pine and loblolly pine which were moderately infected by brown-spot disease. After 3 growing seasons, most stock trees were severely infected, but there were 21 of 47 clones of slash pine out of infection or slightly infected.