The APZ questionnaire was developed in order to explore hypotheses on
ASCs. First - in a series of 11 experiments using different induction
methods on N=393 healthy subjects - the hypothesis was tested that ASC
s have major dimensions in common irrespective of the mode of their in
duction. In the International Study on Altered States of Consciousness
(ISASC) the external validity of the experimental results was assesse
d. The ISASC was carried out on a total of N = 1133 subjects in six co
untries. The main results of the experimental studies were corroborate
d in the field studies. The results can be summarized as follows: the
common denominator of ASCs is described by three oblique dimensions, d
esignated as ''Oceanic Boundlessness (OSE)'', ''Dread of Ego Dissoluti
on (AIA)'' and ''Visionary Restructuralization (VUS)''. The reliabilit
y and validity of the scales are satisfactory. Tested versions of the
APZ scales are available in English (UK, USA), German, Italian and Por
tuguese. Psychometrically as yet untested versions exist in Dutch, Fin
nish, French, Greek, Spanish and Russian. The APZ questionnaire has be
come the international standard for the assessment of ASCs, thus helpi
ng to integrate research. A psychometrically improved version exists i
n German (OAV questionnaire). The BETA questionnaire, which measures t
he dimensions ''Vigilance Reduction (VIR)'' and ''Auditive Alteration
(AVE)'' is also available in German. These dimensions are most likely
etiology-dependent.