This paper describes ACSL, a continuous system simu lation language designed to help the engineer or scientist with a mathematical model analyze the behavior of his system. The computer calculates dynamic responses and interactively provides pictures (plots) and tabular display of selected variables. The user has a choice of two Runge-Kutta integration algorithms and two variable stepsize algorithms which includes Gear's implicit method for stiff sys tems. Any other programmable algorithm can be readily incorporated. The main features of the lan guage are illustrated by a detailed example.