SUMMARYIn this paper we consider a system of two integro-di erential evolution equations coming from a conservative phase-ÿeld model in which the principal part of the elliptic operators, involved in the two evolution equations, have di erent orders. The inverse problem consists in ÿnding the evolution of: the temperature, the phase-ÿeld, the two memory kernels and the time dependence of the heat source when we suppose to know additional measurements of the temperature on some part of the body . Our results are set within the framework of H older continuous function spaces with values in a Banach space X . We prove that the inverse problem admits a local in time solution, but we are also able to prove a global in time uniqueness result. Our setting, when we choose for example X = C( ), allows us to make additional measurements of the temperature on the boundary of the body .