Fir trees growing in areas contaminated by fluorine exhalations show clearly signs of a chronic injury leading finally to the death of the trees. In such contaminated areas individual trees show different degrees of susceptibility and resistance. In contaminated fir stands the disappearance of primary, monophagous bark beetles of the genus Pityokteines Fuchs was noted; while Pissodes piceae Ill. and the twig inhabiting bark beetles Cryphalus piceae Rtzb. C. abietis Rtzb. and Pityophthorus pityographus Rtzb. remained in small numbers. A population increase, however, occurred in Dreyfusia piceae Rtzb., D. nuesslini C.B. and in the wood-wasp Panrurus juvencus L.