A set S of vertices in G is a semitotal dominating set of G if it is a dominating set of G and every vertex in S is within distance 2 of another vertex of S. The semitotal domination number, γ_(t2)(G), is the minimum cardinality of a semitotal dominating set of G. The semitotal domination multisubdivision number of a graph G, msd_(γ_(t2))(G), is the minimum positive integer k such that there exists an edge which must be subdivided k times to increase the semitotal domination number of G. In this paper, we show that msd_(γ_(t2))(G) ≤ 3 for any graph G of order at least 3, we also determine the semitotal domination multisubdivision number for some classes of graphs and characterize trees T with msd_(γ_(t2))(T) =1,2 and 3, respectively.
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