This article concentrates on the validity and reliability of portfolio assessment as used
in pre-service teacher education. It is not possible to make general pronouncements
about the validity of portfolio assessment in pre-service teacher education as there
are multiple portfolio applications. The validity depends on the purpose, namely the
divers competencies which the course organisers wish to assess with it. Therefore,
three categories of competencies and consequently three types of portfolios were
distinguished in order to determine the validity of portfolio assessment. For the
assessment of teaching and partnership competencies, it is argued that the validity is
low due to the roundabout nature of the assessment. On the contrary, the validity of
portfolio assessment for learning competencies can be high. The execution of a selfregulated
learning process can be accurately assessed using portfolios. The reliability
of portfolio assessment is problematic, since it is incapable of fulfilling the classic
psychometric requirement of reliability. Nevertheless, provided that the necessary
measures are taken, the reliability of portfolio assessment can still be brought to an
acceptable level. Five measures are proposed.