Abstract: Anti-theft device for spectacle frames comprising a housing (10) forming an opening (18) to receive therein one bow (34) of the spectacle frame. By clamping means (26) in the housing this can be fastened to the bow. The clamping means has a rotatable operating member, which is accessible in a socket (14) provided on the housing, and can be actuated only by using a special tool. The housing is dimensioned to allow, when fastened to the bow, that the spectacle frame is tried on and that the bow is folded. It is divided into two parts in a plane through the socket. A washer (23) provided with an alarm element for affecting a magnetic, acoustic or electromagnetic field, is pushed onto the socket receiving said socket in an opening in the washer for keeping the two parts of the housing together, and is locked against withdrawal from the socket.