On the sign of the πρω coupling constant

It is shown that the relative sign between the NNω and πρω coupling constants can be determined most sensitively from ω production processes in NN collisions. Recent data on these reactions clearly favor the sign of the πρω coupling constant which is opposite to that inferred from studies of the photoproduction reaction in combination with the vector meson dominance assumption and used by many authors. Implication of this finding in the description of other reactions is discussed.