Abstract: A mirror mounting arrangement for a gas laser, in which the end faces of the laser body are ground and polished to the required accuracy and form direct seatings for the end mirror. The mirror is mounted in an annular frame having an external thin flange remote from the mirror position. This flange confronts a similar flange fixed on to the laser body, the two flanges being separated by an annular gap. A double flanged spacer element which is fractionally shorter, axially, than the gap is inserted in it and welded to the adjacent flanges under axial pressure. The mirror is thus permanently urged into engagement with the laser body end face and its position and attitude fixed. The remoteness of the welding seam avoids damage to the mirror.