In the paper under review the relationship between passivity of quantum field state and the microlocal spectrum condition for free quantum fields on a stationary, globally hyperbolic spacetime is studied. Passive states generalize ground states and KMS states and may be viewed as good candidates for physically realistic states of any dynamical system. The main result shows that a passive state on a Borchers algebra fulfills the microlocal spectrum condition. Also, it is shown that passive states of a topological *-dynamical system have an asymptotic pair correlation spectrum of specific type.