1 . The temporal and spatial distribution of parasitism in Epinotia tedella was investigated within two spruce stands.2. Most eggs were laid by the host female early in the season. The parasitoid, Pimploptenrs dubius, was subjected to a temporal stress, and it also exhibited a greater oviposition rate early in its life. The temporal distribution of attack frequencies by P.dubius and Apanteles tedellae showed a good adaptation to the phenology of the host.3. The spatial distribution of flight activity indicated a preference to exposed sub-habitats by P.dubius and to dark and sheltered sub-habitats by A.tedellae. The distribution of host larvae showed an aggregation in the lower and central parts of the canopy, and so did the attacks by A.tedelZaeeven more pronounced. The attacks by P.dubius showed a slightly inverse aggregation pattern. Apparently, the distribution of attacks was caused by preference to physical conditions, rather than local host densities.4. The decreasing log. area of discovery on increasing log. parasitoid density is obviously a 'pseudo-interference' phenomenon caused by the aggregation of A.tedellae, and temporal asynchrony in P.dubius. 5 . P.dubius dominated in young stands and its importance decreased with increasing age of the stands. The importance of A.tedellae was greatest in stands between 20 and 40 years old, and it dominated in those stands that were especially dense and dark, due to absent thinnings. Correspondence: Dr M. Miinster-Swendsen, Institute of General Zoology, University of Copenhagen, 15 Universitetsparken, DK-2100 Copenhagen 9, Denmark.high compared with the fertility of the host, and since the parasitoids may exert a regulatory effect on the host population.The complex of parasitoid species associated with E.tedella and the phenology and interrelations of the species involved are described by Miinster-Swendsen (1 979a). The host larvae are attacked by four primary parasitoids, two kleptoparasitoids and one hyperparasitoid species. Two primary parasitoids, Pimplopterus dubius (Hgn.) (Ichneumonidae) and Apanteles tedetlae Nix. (Braconidae), predominate within this cornplex and the present work is confined to these two species.