Electronic Journal of Differential Equations, Conference 05 (2000), pp. 91-102. Title: A Lyapunov function for pullback attractors of nonautonomous differential equations. Authors: Peter E. Kloeden (Johann Wolfgang Goethe Univ., Frankfurt, Germany) Abstract: The contruction of a Lyapunov function characterizing the pullback attractor of a cocycle dynamical system is presented. This system is the state space component of a skew-product flow generated by a nonautonomous differential equation that is driven by an autonomous dynamical system on a metric space. Published October 24, 2000. Math Subject Classifications: 34D20, 34D45. Key Words: Lyapunov function; nonautonomous system; pullback attractor.