AbstractFrom a given composite graph two graphs are derived, which can be interpreted as current and voltage graphs, respectively. It is shown that a complete tree of both graphs is a directed tree of the composite graph. Thus the generation of directed trees is reduced to the generation of complete trees. The matrix belonging to the composite graph is decomposed in the incidence matrices of the current and voltage graphs and in a diagonal matrix whose elements are given by the edge‐weights of the composite graph. The number of directed trees in a composite graph is determined using the incidence matrices of both graphs.