Transversal ultra-structure and firmness were examined on cooked spaghetti-shaped pasta prepared from durum semolina with 0% (control), 10%, 20%, and 30% Alaskan pollock surimi. The ultra-structure of the pasta exhibited two differences between inner and outer gross structures of the extruded product. In the inner portion, control and surimi-added pasta were not different. In the outer portion, surimi gel was observed as a network with small cavities uniformly distributed throughout the matrix formed by the gluten and/or gelatinized starch of durum semolina. Cooked firmness of the pasta decreased with addition of surimi.