Using Nimbus-7 Total Ozone Mapping Spectrometer (TOMS) data, this article discusses the seasonal variation in total ozone over the Tibetan Plateau. In addition, total ozone trends over this region are revealed by linear regression analysis. Low ozone concentrations are found over the large scale topographies of the Tibetan Plateau, the Rocky Mountains, and the Andes Mountains. The phenomenon is the strongest over Tibet. Total ozone in Tibet is lowest in October and highest in March. However, relative to zonal mean total ozone, largest ozone deficiency over Tibet occurs in May, while smallest deficiency occurs during November--January months. The ozone deficiencies are negatively correlated to the heat flux from the surface to the air in Tibet, with correlation coefficient -0.97. The ozone trend over Tibet, deduced from TOMS 1978--1991 year-round data, is -0.79¿0.82 DU/Year (-2.7¿2.8 percent/decade), with the monthly trends ranging from -0.17 DU/year (-0.6 percent/decade) to -1.79 DU/year (6.0 percent/decade). ¿ American Geophysical Union 1996