During the period of 1960 till 1986 the animals present in about 1.200 churches in the Netherlands have been investigated by the author of this article and some of his colleaques. In many churches either bats or Barnowls were present. In 131 buildings these animals were living there in the same time but in 57 of the buildings they used seperate rooms (f.i. a Barnowl in the tower and a number of serotines on the loft). In only 17 out of the 75 churches were Barnowls and bats shared the same quarters, no declining numbers of bats were registered during repeated controles. In the other 57 buildings the bats either vanished or declined. Sometimes abandoned strongholds of bats were used again after the Barnowls had disappeared. In two other churches were bats and Tawnyowls temporary lived together, the same kind of interactions were registred. These results are in accordance with what might be expected, because biologists have proved that of nearly all kinds of European owls individuals occasionally hunt on bats and that of nearly all European batspecies remnants have been recovered in owl-pallets. It is suggested that even unsuccesfull hunting-attemps of owls may cause removals of bats.