Sodium fluorescein staining of the retina following fluorescein angiography may affect the absorption characteristics of argon ion laser photocoagulation. This hypothesis was investigated by performing laser photocoagulation on control and fluorescein stained porcine retinas. The resultant damage was viewed by scanning electron microscopy. In both specimens, argon irradiation produced damage to the pigment epithelium and overlying photoreceptor layer. The control sample showed a deep cylindrical burn, indicative of internal heating, in both retina and choroid. The fluorescein stained sample showed damage consistent with thermal interaction from the surface downwards leaving the choroid relatively spared. This preliminary study demonstrates that fluorescein staining of the retina changes the absorption site of argon laser light and this subject clearly merits further investigation.