Abstract: The amount and role of Hendersonia acicola Tub. in the epidemic caused by Lophodermella sulcigena (Rostr.) v. Hohn. was followed on Scots pine (Pinus sylvestris L.) in Finland. From year to year H. acicola increased on needles primarily infected by L. sulcigena up to the end of the Lophodermella epidemic. Hendersonia was first abundant in the lower crown, while the upper parts were nearly free of it. The increase of H. acicola prevented L. sulcigena from producing ascocarps and led to the recovery of the trees and stands. L. sulcigena could fruit only in those needles which were free of H. acicola in the autumn. The autumnal presence of H. acicola in the needles led to a natural control of the pathogen. Experiments with H. acicola showed that it is possible to develop biological control against L. sulcigena.