This paper contains a description of an interactive computer program developed for use in water quality analysis and management of a river basin. This Interactive Water Quality Analysis And Management (IWQAM) program is written in FORTRAN and designed for use on an IBM or compatible Personal Computer. The IWQAM program consists of: 1) a simulation model to calculate dissolved oxygen (DO) concentrations in a river basin (the model is based on the Streeter-Phelps equation); 2) a utility subroutine to formulate a least-cost linear programming model to meet a specified DO standard for the river basin; 3) a subroutine with a Simplex algorithm to search for the least-cost treatment solution for the formulated model in part 2; and 4) a main program to handle the user-computer interactions. This program was developed originally for the use by students in a water quality management course. Because of the interactive nature of the program, it can be used by students who have limited experience in programming. Its major feature is that it can be used to conduct sensitivity analyses on parameters that affect the DO concentrations in the river. Furthermore, it permits the interface between the DO simulation model and the least-cost optimization model, so that various management alternatives can be examined with respect to treatment costs and the DO levels in a river basin.