The authors retrospectively studied 32 neonates with macrocrania associated with a pericerebral collection. Differential diagnosis was made between external communicating hydrocephalus, atypical communicating hydrocephalus, subdural hygroma and local cerebral atrophy by means of CT scan, isotope cisternography, and isotope brain scintigraphy. Especially the two last examinations are of great interest. The most important arguments in favour of operation were a rapidly increasing and uncontrolled head circumference graph and a deterioration of the psychomotor development. In this regard, 13 out of 25 patients with external communicating hydrocephalus were operated upon (lumbo-peritoneal shunt). The analysis of the results reveals that rapidly increasing macrocrania is a good operative indication and gives excellent results but psychomotor deterioration turned into normal evolution only in 14% of the operated cases. Evacuation of a subdural hydroma first by external and followed later on by internal drainage normalizes the clinical picture.