SummaryThe importance of oxygen administration in regard to the manifestation of changes in the calibre of the retinal vessels as well as the presence of peripheral retinal oedema has been studied from a material of 130 premature infants. It appears that the retinal vessels were often very narrow during the administration of oxygen, and that vascular dilatation and peripheral oedema occurred in most cases when oxygen was stopped, but, in individual cases, even whilst oxygen was being administrated. In the eases that had not been given oxygen, dilatation of the vessels and oedema occurred immediately after birth. Of those that were treated with oxygen, 2 developed into re‐trolental fibroplasia. Finally, attention is drawn to the connection between the time when retrolental fibroplasia made its appearance in different countries as well as the time when incubators with surplus oxygen began to be used in the respective countrie