Using Total Ozone Mapping Spectrometer (TOMS) version-7 level-2 clear-sky (reflectivity ≤20%) ozone measurements corrected for aerosol effects and sea-glint errors, we derived Lower Tropospheric Ozone (LTO) west and east of the Andes, the Mexican and Rocky Mountains, the mountains in Africa and the Arabian Peninsula, New Guinea, and the Himalayan Mountains. The derived results agree reasonably well with the seasonality of LTO from ozonesonde observations at Boulder, Cristobal, Fiji, Java, and Tahiti. The LTO seasonality found in the biomass burning seasons characterized by the ATSR World Fire Atlas west and east of the Andes (23 ¿S--2 ¿N), east of the Mexican Mountains (15¿--23 ¿N), South Sudan (6¿--14 ¿N), South Africa (30¿--28 ¿S), and west of New Guinea is consistent with the influence of biomass burning on the formation of tropospheric ozone in these regions. The significant El Ni¿o influence on LTO west of New Guinea is evident throughout several El Ni¿o cycles. The spring maximum in ozone west of the Mexican Mountains, in western China, and west of the Andes (32¿--23 ¿S) is consistent with a stratospheric intrusion source. East of the Mexican Mountains (23¿--30 ¿N), both west and east of the Rocky Mountains, in north Sudan and Iraq, and in western China, high concentrations of ozone are found in these continental and coastal regions which are affected by anthropogenic sources. The maximum ozone in these regions usually occurs in the summer due to photochemical ozone production. A summer LTO minimum occurs in coastal regions west of the Andes and west of Mexico, due to ozone destruction in low NOx and high H2O marine environment. A summer minimum also occurs in south Sudan in the rainy season. The LTO in the northern tropics of South America (4¿--10 ¿N), Africa (1 ¿S--2 ¿N), and east of New Guinea (7¿--3 ¿S) experiences little seasonal variation. ¿ 2001 American Geophysical Union