First of all seven of our own thoroughly investigated cases of so-called amaurotic idiocies are presented, they are two infantile, two juvenile, two late infantile one, as well as one adult case. The two infantile cases represent the typ of a GM2-gangliosidosis: with cerebral symptoms and cherry-red spot in the macula they correspond clinically to the typical picture of Tay-Sachs disease. Lightmicroscopically they show neuronal storage, electronmicroscopically a deposition of "membranous cytoplasmic bodies" and biochemically a strong increase in ganglioside GM2. The two juvenile cases correspond in their symptoms and findings to the so-called ceroid-lipofuscinoses or "Myoclonic variant of amaurotic idiocy", respectively. Clinically most remarkable is the deterioration of vision caused by retinitis-pigmentosa-like changes of the fundus, which sets in at the beginning of the disease and precedes the cerebral symptoms by years. The extinguished electroretinogramm corresponds in the histological retina findings to a severe lesion of the layer of rods and cones in the sense of a tapeto-retinal degeneration. Neuropathologically finegranular, Sudan-Black-B- and PAS-positive material is mainly but not exclusively stored in the neurons. The electronmicroscope shows them to be lipofuscin-like inclusions, as well as "curvilinear" or "fingerprint-bodies". Depositions are also to be found in astrocytes and in the cells of the vascular walls. The ganglioside pattern is normal in the brain tissue of the biochemically investigated case. Of the two late infantile cases the first represents a GM2-gangliosidosis, the second one corresponds to the ceroid-lipofuscinosis. The adult patient, who suffered from an ill-defined psychiatric disease and died at the age of 51 presents a diagnostically problematic case, showing a relatively slight, regionally rather differently accentuated intraneuronal storage of granular material and biochemically a slight increase in ganglioside GM2. On discussing our own findings and commenting on the relevant literature various aspects of amaurotic idiocies are considered, such as genetics, neuropsychiatry, ophthalmology, pathomorphology and biochemistry. In this respect special attention is paid to the pathomorphological substrate documented, as localization, degree and kind of tissue changes determine the clinical picture. This is also the case for the correlation between the findings of the different fields, so e.g. concerning the ophthalmological findings it is shown, that in gangliosidoses with preserved ERG histologically a storage in the nerve cells of the ganglion cell-layer only is to be found, where as the ceroid-lipofuscinoses with early onset of deterioration of vision and extinguished ERG in the histological picture of the retina show an additional severe lesion of the layer of rods and cones...