During an outbreak of the gypsy moth Lymantria dispar L. (Lep., Lymatriidae) near Offenburg, South-west Germany, in 1984 until 1986, the biology and effectiveness of several primary and secondary parasitoids were investigated in the postculmination phase 1986. Adults of Parasetigena silvestris R.-D. (Dipt., Tachinidae) were most abundant during the larval period of L. dispar. They attached macrotype eggs on second instar and older larvae. In spite of the fact that 50% of these eggs were lost by molting, parasitism raised up to 97%, superparasitism up to 83%. Last instar larvae were parasitized by an average number of 3 maggots, but only one of them developed. They killed their host immediately before pupation. Adults of Blepharipa schineri Mesnil (Dipt., Tachinidae) were also abundant during the larval period of L. dispar. They preferred leave edges damaged by feeding for deposition of microtype eggs. Third instar and older larvae were parasitized. The parasitism raised up to 96%, superparasitism up to 77%. Last instar larvae were attacked by an average number of more than three maggots. They penetrated ganglions of the nervous system but didn't develop before pupation of the host. Only one maggot per host developed. Compared with P. silvestris and B. schineri, Blepharipa pratensis Meigen (Dipt., Tachinidae), Compsilura concinnata Meigen (Dipt., Tachinidae) and Ceranthia samarensis Villeneuve (Dipt., Tachinidae) were rare. They parasitized fourth and higher instar larvae. Low rates of parasitism occurred also by Apanteles melanoscelus Ratzburg (Hym., Braconidae), Apanteles liparidis Bouche, Apanteles porthetriae Muesebeck and Phobocampe disparis Viereck (Hym., Ichneumonidae) in first till fourth instar larvae. Multiparasitism by P. silvestris and B. schineri, raised up to 92%. Keen competition occurred between all species. Species with higher velocity of development succeeded: All Hymenoptera asserted successfully against Tachinidae. Within the Tachinidae C. concinnata and C. samarensis were very successful against P. silvestris, which was also very effective against B. schineri. Planidium larvae of Perilampus spec. penetrated muscular fibres of L. dispar larvae but didn't damage their hosts. Later in the season they attacked primary parasites. A. melanoscelus and A. liparidis were parasitized by Perilampus spec. (Hym., Perilampidae), P. silvestris and B. schineri by Perilampus ruficornis Fabricus. The parasitoids effected the collapse of the gypsy moth population in 1986. none