DYNAMO, a computer language for simulating models of business, economic, social, biological, and engineering systems, allows easy communication with the computer and among modelers. Moreover, it can be mastered by non-programmers in just days. The sixth edition of this popular manual introduces the basic DYNAMO language, includes a reference manual for DYNAMO II with an expanded section on macros, and documents all the improvements that have been made to DYNAMO II since its inception. (Originally published in 1970, reprinted in 1973, 1976, and 1983) Alexander L. Pugh III.