Model-based development is becoming an increasingly com-
mon development methodology. In important domains like
embedded systems already major parts of the code are gener-
ated from models specified with domain-specific modelling
languages. Hence, such models are nowadays an integral
part of the software development and maintenance process
and therefore have a major economic and strategic value for
the software-developing organisations. Nevertheless almost
no work has been done on a quality defect that is known to
seriously hamper maintenance productivity in classic code-
based development: Cloning. This paper presents an ap-
proach for the automatic detection of clones in large mod-
els as they are used in model-based development of con-
trol systems. The approach is based on graph theory and
hence can be applied to most graphical data-flow languages.
An industrial case study demonstrates the applicability of
our approach for the detection of clones in Matlab/Simulink
models that are widely used in model-based development of
embedded systems in the automotive domain.