A new mechanism of pattern formation different from the Turing and oscillatory instabilities in the reaction–diffusion systems was found. It is closely connected with the resonance phenomenon that appears in the models when Jacobi's matrix of the kinetic part is equivalent to Jordan cell and diffusion coefficients are cited. Some results of numerical calculations of the blood coagulation model are discussed. The pattern formation regimes that can be treated as the results from the resonance phenomenon were observed.
