PC BEEPOP is a computer model that simulates honey bee (Apis mellifera L.) colony population dynamics. The model consists of a system of interdependent elements, including colony condition, environmental variability, colony energetics, and contaminant exposure. It includes a mortality module (BEEKILL) and a chemical-toxicity data base (BEETOX). PC BEEPOP builds upon BEEPOP, a mainframe-based colony dynamics model. PC BEEPOP is a research and assessment tool for assessing the responses of honey bees as ecological indicators of environmental condition. The combination of BEETOX, BEEKILL, and BEEPOP provides a means of examining the influence of xenobiotics on colony population dynamics, including energetics, and not just adult or brood mortality. The authors simulations indicate that PC BEEPOP is capable of making plausible predictions of colony structure, size, and energetics. In addition, the model can help identify probable causes of colony growth and decline.