This is a report prepared for the intermediate altitude region (the lower thermosphere, lying between about 100 and 200 km). This region dif fers considerably from the lowest one, in which the volume of data makes statistical methods of analysis appropriate. For the highest region, a considerable amount of satellite data is available and the behavior of the atmosphere is reasonably well understood. Some rocket data is available for the lower thermosphere, but most of the meas uring instruments are experimental and a major part of the data analysis consists in studying the physics of the various corrections or calibra tion factors required. At the upper end of the altitude regime some satellite data is available. New density data includes the results from flights of two types of falling spheres, results from the diffusion of chemical clouds, and data from drag effects on three satellites with perigee altitudes near 200 km. The satellite data indicates a de pendence of density on the value of the magnetic A sub p index. Otherwise, the data shows more variation with the method of measurement and data reduction than actual variation of the atmosphere. (Author).