The authors give an account of 12 patients where the original ophthalmological finding corresponded to central serous retinitis. In the course of check-up examinations the picture changed and finally the complex of applied examinations revealed that a malignant melanoma of the choroid was involved. The authors mention the time needed for the clinical decision on the final diagnosis of the disease which was confirmed histologically after enucleation of the eye. In the conclusion the authors draw attention to the necessity of frequent check-up examinations after the initial establishment of the diagnosis of central serous retinitis with regard to the differential diagnostic possibilities of the above disease.