We propose a Monte Carlo algorithm which accommodates an unbiased stochastic estimates of the fermion determinant and is exact. This is achieved by adopting the Metropolis accept/reject steps for the update of both the dynamical and noise configurations. We demonstrate how this algorithm works even for large noises. We also discuss the Padé - Z2 estimates of the fermion determinant as a practical way of estimating the Trln of the fermion matrix.