The average drag on the LAGEOS satellite appears to be well understood. It consists of three types of drag: Yarkovsky thermal, neutral particle, and charged particle. Yarkovsky thermal drag depends on the LAGEOS spin axis position. The spin axis in the decade since launch appears to have stayed near where the engineering telemetry data put it at apogee kickmotor separation: 22¿ colatitude and 313¿ east longitude. This result is based on fitting more than 11 years of along-track acceleration data to a thermal model. The Center for Space Research at the University of Texas has obtained a similar answer. For this position, Yarkovsky thermal drag accounts for about 70% of the observed drag. Neutral particle drag accounts for about 14% of the drag for a hydrogen number density of 5¿109 m-3. Proton drag accounts for 12 per cent at a number density of 3¿109 m-3 and a temperature of 5000 K in the plasmasphere for a satellite potential of -1 V. Charged helium and oxygen give another 4%, so that charged particle drag totals 16%. All together the three types of drag account for all of the observed average drag. Hence there is closure: the particle environment at LAGEOS altitude, the drag models, and the observed drag are all consistent with each other. Less well understood are the fluctuations in LAGEOS's along-track acceleration when the orbit intersects the Earth's shadow. ¿ American Geophysical Union 1990