One big question that overshadows any efforts to use chips as mulch is whether or not those chips?-?if from a diseased tree?-?pose any threat to the health of the trees that are otherwise expected to benefit from the treatment. A limited number of experiments to confirm that chips infested with pathogenic fungi do, in fact, pose a threat to plant health generally support the contention that chips from diseased trees are “safe” if they are properly composted. The diseases have been studied in this context are Verticillium wilt, Armillaria root rot and Phytophthora. The term “proper” composting is discussed. After having looked at what is an admittedly thin amount of reliable data, the conclusion is that it’s probably wise to err on the side of caution with regard to use of fresh waste wood chips.