As a logical consequence to an extensive investigation concerning the development of the electroencephalogram in normal children up to 16 years by PETERSÉN and EEG-OLOFSSON (1971), this study was undertaken to describe the development of the electroencephalogram during the rest of the “growing up” period. The age period investigated was 16 through 21 years. The investigation was carried out as a transverse study and comprises EEG examinations on 185 adolescents — 94 females and 91 males. The selection of subjects is based on the same criteria of normality as described by the aforementioned authors. The subjects were collected from common schools, trade schools, schools for education of nurses, physiotherapists, and secretaries, as well as military and municipal institutions. The material is described with regard to start of puberty, birth oder, and social family data. EEG was recorded at rest, during hyperventilation, and intermittent photic stimulation in all subjects. Sleep activation was successful in all but one female, who, however, attained deep drowsiness. The results are presented in tables which have been supplemented by comments and significant correlations. The amount of non-rhythmic low frequency activity was estimated in the resting records, which were classified as having “minute” (“supernormal” EEG), “normal” (“normal” EEG), “slightly increased”, and “moderately increased” amount of low frequency activity. The two last-mentioned findings occurred at 4.9 per cent and significantly more often in females than in males. Observed rhythmic patterns at rest were slow alpha variant, polyphasic potentials, 5–6 Hz activity in (temporo-) occipital derivations, 6—7 Hz activity in anterior derivations during drowsiness, and mu rhythm. The most common response to hyperventilation was the appearance of mainly non-rhythmic low frequency activity (mainly theta activity) in posterior derivations. In addition there were responses which were confined to anterior derivations as delta waves, or which occurred diffusely as theta/or delta waves. The mean persistence of response after termination of hyperventilation did not last longer than about 50 sec. as regards the posterior effect. The mean persistence of delta activity was about 16 sec. During intermittent photic stimulation the photic driving response was confined to low frequencies (not exceeding 6 Hz) in 8 per cent and to high frequencies (20 and 24 Hz) in 25 per cent. Spontaneous sleep was achieved in 63 per cent of the subjects. Paroxysmal effects, with the exception of the 14 and 6 Hz positive spike phenomenon, psychomotor variant pattern, and 6 Hz spike-and-wave phenomenon, were found in 9 subjects (4.9%) — 2 cases showing a paroxysmal response during both intermittent photic stimulation and sleep. Seven of the mentioned cases had a “normal” resting record. Most paroxysmal responses occurred sporadically and were of an equivocal character. There was no significant age or sex relation. The 14 and 6 Hz positive spike phenomenon (14–6-PS) occurred in 27 subjects (14.6%) without significant age or sex relation. The bursts appeared sporadically and with short duration. Psychomotor variant pattern was found in 2 cases (1.1 %) and 6 Hz spike-and-wave phenomenon in 7 cases (3.8 %). In comparison with normal children, there were in general a lower incidence and less prominence of different EEG findings in normal adolescents; this “levelling off” was most apparent after the age of 18 years. The only sex differences found were confined to the incidence of slight and moderate increase of low frequency activity, which was higher in females than males, and the expression of beta activity with a preponderance for females. Thus in normal adolescents in the ages from 16 through 21 years there are fewer differences in regard to sex and no age dependence in comparsion with results obtained with normal children. This may be an expression of a tapering off of a maturation process and according to the present results the maturation as seen in the electroencephalogram is suggested to have terminated by the end of the investigated age period. Diese Arbeit stellt die logische Fortsetzung einer ausführlichen Untersuchung der hirnelektrischen Entwicklung bei normalen Kindern bis zum Alter von 16 Jahren dar (PETERSÉN und EEG-OLOFSSON 1971) und beschreibt die Entwicklung des Elektroenzephalogramms während des letzten Abschnittes der Entwicklungsperiode zwischen dem 16. und dem 21. Lebensjahr. Sie wurde in Form einer Querschnittsuntersuchung durchgeführt und basiert auf den Ergebnissen von EEG-Ableitungen bei 185 Adoleszenten — 94 weiblichen und 91 männlichen. Bei der Auswahl der Versuchspersonen wurden die gleichen Kriterien für Normalität wie bei den vorhergehenden Untersuchungen angewendet. Die Versuchspersonen kamen aus allgemeinen Schulen, aus Handelsschulen, aus Schulen für Krankenschwestern, Krankengymnastinnen und Sekretärinnen, außerdem aus militärischen und städtischen Einrichtungen. Das Patientengut wurde im Hinblick auf Alter beim Eintritt der Pubertät, Stellung in der Geschwisterreihe und soziale Gegebenheiten aufgegliedert. Die EEG-Ableitungen wurden bei allen Versuchspersonen in Ruhe, unter Hyperventilation und unter intermittierender Fotostimulation durchgeführt. Schlafaktivation konnte bei allen Versuchspersonen, mit Ausnahme einer weiblichen, durchgeführt werden, bei der es lediglich zu starker Müdigkeit kam. Die Ergebnisse wurden in Form von Tabellen, ergänzt durch Anmerkungen und Hinweise auf signifikante Korrelationen, dargestellt. Die Häufigkeit nicht-rhythmischer niederfrequenter Aktivität in den Ruheableitungen wurde geschätzt, die Ableitungen wurden entsprechend als solche mit...