The simplicity of the two-symbol activity cycle diagram (ACD) has made it easy to learn and use to describe discrete event systems in a natural way. But as the complexity of the model increases, the ability of the ACD to provide a full description of the system under consideration becomes more limited. This paper presents an extended ACD with arc attributes and its formal definition to increase the modeling power of the ACD. The validity of the proposed extensions is shown by proving the generality of the extended ACD, which has not yet been done on the ACD. In addition, this paper proposes a model specification for the simulation execution of the extended ACD models which we call the activity transition table (ATT). At last, the simulation software tool is presented to support model implementation, model execution, and experimentation for the extended ACD models. (C) 2010 Elsevier B.V. All rights reserved.