Optical coherence tomography (OCT) allows for morphological assessment of macular edema of various origins by producing two-dimensional images of the retina. In addition, retinal thickness can be measured quantitatively. In diabetic maculopathy, damage of the blood-retinal barrier can be indirectly assessed by locating the intraretinal fluid accumulation and the progress of maculopathy from diffuse to cystoid edema and even rupture of the retinal structure can be described as well as the formation of neurosensory retinal detachment with subretinal fluid. Increase of retinal thickness correlates with decrease in visual acuity. Detailed interpretation of OCT images can replace fluorescein angiography in certain cases, as has been shown for uveitis. In order to obtain correct classification of macular disease in routine clinical use, all images have to be completely assessed and compared to previous investigations and to the measurements of the fellow eye. More accurate normal values of retinal thickness and volume can be expected in the future. The importance of OCT in routine clinical assessment of macular edema will most probably continue to grow.