LOWTRAN 7 is a low-resolution propagation model and computer code for predicting atmospheric transmittance and background radiance from 0 to 50,000 cm -1 at a resolution of 20 cm -1. The code is based on the LOWTRAN 6 (1983) model. Multiple scattered radiation has been added to the model as well as new molecular band model parameters and new ozone and molecular oxygen absorption parameters for the UV. Other modifications include a wind dependent desert model, new cirrus cloud models, and new cloud and rain models. The code also includes new representative (geographical and seasonal) atmospheric models and updated aerosol models with options to replace them with user-derived values. An improved extra-terrestrial solar source function is also included. Six modes of program execution are allowed with the new model and computer code for a given slant path geometry. This report contains a description to users for operating the LOWTRAN 7 computer code. It summarizes the capabilities of the new code, provides complete operating instructions as well as input and output from test cases for user validation. Also included are operating instructions for three programs that utilize LOWTRAN 7 output (plot, filter and scanning function programs).