PTPLU is a point source dispersion Gaussian screening model for estimating maximum surface concentrations for 1-hour concentrations. PTPLU is based upon Briggs' plume rise methods and can use either Pasquill-Gifford or Briggs' urban dispersion coefficients. PTPLU is an adaption and improvement of PTMAX which allows for wind profile exponents and other optional calculations such as buoyancy induced dispersion, stack downwash, and gradual plume rise. PTPLU produces an analysis of concentration as a function of wind speed and stability class for both wind speeds constant with height and wind speeds increasing with height. Using the extrapolated wind speeds and the options allows the model user a more accurate selection of distances to maximum concentration. PTPLU1 is the interactive version of the model. Software Description: The model is written in the FORTRAN programming language for implementation on an IBM 3090 computer. The software is distributed on a 5 1/4-inch IBM/PC-compatible diskette. Data is in compressed format but a dearchive utility is included.