In the analysed material of 55 cases of subdural hygroma in children the authors found that the hygroma was most frequently a complication of inflammatory conditions of the central nervous system and diarrhoea. The analysis showed that recurrent vomiting, febrile states, failure to thrive should be an indication to diagnostic investigations for subdural hygroma. The simplest and most useful method is transillumination of the skull which was positive in 84% of cases.