The gangliosidoses belong to the family of diseases known as the lipidoses and are due to an excess of ganglioside I (GM1) or II (GM2). The illness described by Landing belongs to Group I, whilst Tay-Sachs and Sandhoff's disease are type 2. This study was particularly concerned with the electro-clinical aspects of group 2, and 4 stages have been differentiated: --the first occurs between 4-10 months: the child is apathetic, hypotonic and has occasional audiogenic seizures; fundoscopy revealing the classical cherry red spot on the macula. The diagnosis can be confirmed by biopsy. The EEG is irregular but abnormalities are minor. --the second stage (10 months-2 years) the child spastic and amaurotic, often unresponsive is suffering from frequent seizures. The EEG is of high voltage, with slow and sharp waves. Auditory stimulation does not produce EEG changes. --in the third and 4th stages (after 2 years) the child is in a vegetative state with a progressive reduction in EEG voltage and sharp waves until death aged 3 or 4. Although there is a good correlation between clinical signs and EEG this is of no diagnostic value.