Abstract Stem and root rot of Douglas fir, Pseudotsuga menziesii (Mirb.) Franco. In 20 year old Douglas fir most of the butt rot was caused by Fomes annosus . Stem decay was central as well as eccentric reaching the sap wood in either case. The side roots of 20 year old Douglas fir were compared with those of a 40 year old stand with butt rot. In individual trees with decay there were less roots with Fomes annosus decay in the younger stand. Calocera viscosa was more abundant in the older stand. Soil conditions which might have favoured root rot in the young stand are discussed.