  We investigate the short distance behavior of 3 nucleon forces (3NF) defined
through Nambu--Bethe--Salpeter wave functions, using the operator product
expansion(OPE) and calculating anomalous dimensions of 9--quark operators in
perturbative QCD. As is the case of NN forces previously considered, we show
that 3NF have repulsions at short distance at 1--loop, which becomes exact in
the short distance limit thanks to the asymptotic freedom of QCD. Moreover
these behaviors are universal in the sense that they do not depend on the
energy of the NBS wave function for 3 nucleons.
