This interactive computer graphics system permits biologists to study models of kinetic chemical systems and computer scientists to investigate interactive modeling. The program runs on an IBM 360/40 computer and is intended to provide a convenient means of (1) describing a model via chemical equations; (2) observing the behavior of a model during simulation; and (3) editing output formats and modifying the model. The user communicates with the computer via the RAND Tablet used in conjunction with a 2250/Model 1 CRT display device. The program has several desirable features. (1) It simulates multiphase chemical systems having both fast and slow reactions. (2) The user may enter chemical equations by printing them, as on a piece of paper, and the program displays its interpretation as a check. (3) The user can intervene in the simulation at any time, examine any reactant plotted on any linear scale against any other reactant or time, rescale curves, or delete them. (4) A reset capability permits backtrack for correction or to return a graph to a previous state.