The VALLEY algorithm is a steady-state, univariate Gaussian plume dispersion algorithm designed for estimating either 24-hour or annual concentrations resulting from emissions from up to 50 (total) point and area sources. Calculations of ground-level pollutant concentrations are made for each frequency designated in an array defined by six stabilities, 16 wind directions, and six wind speeds for 112 program-designed receptor sites on a radial grid of variable scale. Empirical dispersion coefficients are used and include adjustments for plume rise and limited mixing. Plume height is adjusted according to terrain elevations and stability classes. Software Description: The software is written in the FORTRAN programming language for implementation on an IBM model 3090 computer. The model is distributed on a 5 1/4-inch IBM/PC-compatible diskette. Data is in compressed format but a dearchive utility is included.