This paper considers an average consensus problem for multiple integrators over fixed, or switching, undirected and connected network topologies. Event based control is used on each agent to drive the state to their initial average eventually. An event triggering scheme is designed based on a quadratic Lyapunov function. The derivative of the Lyapunov function is made negative by an appropriate choice of the event condition for each agent. The event condition is sampled-data and distributed in the sense that the event detector uses only neighbor information and local computation at discrete sampling instants. The event based protocol design is illustrated with simulations. (C) 2013 Elsevier Ltd. All rights reserved.