The Cotton and Insect Management (CIM) model was developed at Mississippi State University during the 1970's as a simulator to study cotton insect management strategies. CIM includes interacting models of the cotton crop (COTCROP), boll weevil (Anthonomous grandis) (CIM-BW), and heliothine (Heliothis virescens and Helicoverpa zea) populations (CIM-HEL). Variable effects of insecticides on boll weevil and heliothine populations and variable effects of beneficial insects on heliothine populations are included in the insect models. CIM has recently been revised to run in a Windows environment on personal computers (PC's). Typical simulation time is ~ 3 seconds on a pentium computer. In the early 1980's, a single simulation on the mainframe UNIVAC 1100/80 at Mississippi State University required 2 - 5 minutes. The new PC version of CIM uses a spreadsheet format for manipulating input and output data. The increased speed of simulation, the user friendly interface, and the experimental flexibility of the spreadsheet approach makes the model more accessible to researchers and pest managers interested in simulation experiments of the interaction between cotton and cotton insects. Future plans are to sophisticate the simulation capabilities of CIM by adding routines for generalized herbivores and increasing the detail of the insecticide, damage, and natural mortality subroutines that can be manipulated via the spreadsheet interface. Experiments can then be conducted with a broader pest complex exposed to a wider range of management options. We expect this refined CIM to be an important component of our research planning and management.