Dynamic theological properties were investigated during gelation of chicken myofibrillar protein as influenced by heating procedures, Thermal scan (1 degrees C/min) of myofibril suspensions in 0.6M NaCl (pH 6.0) induced a major transition in storage modulus (G', peak 48 degrees C), preceded by a transition in protein-protein aggregation (46 degrees C) and accompanied by a marked reduction in actomyosin solubility. Preheating at 50 degrees C diminished the transition and resulted in increased final G' value. Isothermal heating produced complex, temperature-dependent theological changes (G' and phase angles), particularly within 43-58 degrees C. The theological transitions of myofibrillar protein were probably related to kinetic changes during formation of elastic gel networks. Such rheological data on gel formation can help predict and control muscle food responses to specific thermal processes.