Ips acumiinatus (Gyllenhall) and Tomicus piniperda (L.) were the main scolytid beetles in Scots pine, Pinus sylvestric L., outbreak areas near Orleans, France during 1978-1979. Ips acuminatus attacked thin-bark logs while T. piniperda attacked thick-bark logs. More than 150 species of insects were associated with these scolytids. Forty-five species (31 predators and 14 parasitoids) were confirmed as natural enemies of bark beetles. Three predators were abundant: Thanasimus formicarius L. (Col.: Cleridae), Rhizophagus depressus (F.) (Col.: Rhizophagidae) and Medetera spp. (Kipt.: Dolichopodidae). The first two were especially frequent in galleries of T. piniperda, while Medetera spp. were more abundant in galleries of I. acuminatus. The main parasitoids were Rhopalicus tutela (Walker) and R. brevicornis Thomson (Hym.: Pteromalidae), Coeloides abdominalis Zetterstedt and C. melanostigma Strand, Dendrosoter middendorfi Ratzeburg and D. hartigii Ratzeburg, and Spathius rubidus Rossi (Hym.: Braconidae). These parasitoids are polyphagous. However, C. abdominalis was obtained from T. piniperda but not from I. acuminatus, while S. subidus and D. hartigii were obtained from I. acuminatus but not from T. piniperda. Temporal and relative abundance of natural enemies of T. piniperda and I. acuminatus were studied. The predators R. depressus and T. formicarius had complementary limiting effects on bark beetles as adults and larvae of R. depressus fed mainly on scolytid eggs, while T. formicarius adults attacked scolytid adults and the clerid larvae preyed upon scolytid larvae. The predatory pressure applied by T. formicarius and R. depressus to T. piniperda early during the spring was later complemented by a series of parasitoids and other predators. This sequential timing of the natural enemies of T. piniperda suggests that the interactions among the gild are more complementary than adverse. Differential timing of the natural enemies in logs infested by I. acuminatus and some evidence of competition between the predators Medetera spp. and parasitoids suggested a less effective control of this scolytid. Number and duration of larval instars were determined, and measurements of predatory activity were made for Thanasimus formicarius, Rhizophagus depresus, Hypophloeus fraxini Kugelann (Col.: Tenebrionidae), Platysoma fronale Paykull (Col.: Histeridae), and Xylocoris cursitans (Fallen) (Het.: Anthocoridae). Predatory activity was evaluated for last instar larvae and adults of Scoloposcelis obscurella (Zetterstedt) (Het.: Anthocoridae), and for last instar larvae of Medetera sp. and Lonchaea collini Hackman (Dipt.: Lonchaeidae). none