During simultaneous testing of electro-encephalograms and pneumoencephalograms in 200 children of various ages a proven correlation of statistics between both test procedures emerged as a well-defined parameter for evaluation. When making a statement about the correlation in findings between E.E.G. and P.E.G. the age of development in a child must be taken into consideration. Thus it emerged that in infants pronounced enlargement of the ventricular system correlates with active tension E.E.G. at increased inter-cranial pressure, while the coincidence of focal changes in E.E.G. and P.E.G. with advancing years becomes at first more pronounced after the tenth year of life (or puberty) but afterwards lessens.