Heat-induced gelation properties of brown trout crude myofibrils and of myofibrillar proteins (salt soluble) from white and red muscles were analysed by thermal scanning rheometry. Rheological characteristics of myofibrillar protein were similar to those of myofibrils, regardless of the muscle type. For both myofibrils and myofibrillar protein, stronger gels were observed at low pH values (5.6 vs. 6.0) and low ionic strength (0.2 M vs. 0.6 M KCl). Interaction of 1 2 3 * Station commune de recherches en ictyophysiologie, Biodiversité et environnement, Institut national de la recherche agronomique, Campus de Beaulieu, 35042 Rennes cedex, France. Institut de Recerca i Tecnologia Agroalimentaries, Centre de Tecnologia de la Carn, Granja Camps y Armet, 17121 Monells, Girona, Spain. Station de recherches sur la viande, Institut national de la recherche agronomique de Theix, 63122 StGenès Champanelle, France. Correspondence lefevre@beaulieu.rennes.inra.fr myofibrillar proteins and that of myofibrils occurred at lower temperatures in white muscle (starting at 20°C) than in red muscle. Gels observed after gradual heating to 80°C were equally strong and elastic for both muscle types.