Characteristics of the tropical tropopause are described using radiosonde observations in Indonesia. Annual cycles of tropopause height are clearly seen and year-to-year variations are also recognized, especially the in the rainy seasons. Over Indonesia, the tropopause is colder and located higher than that over western Pacific. Cross spectral analyses indicates that the minimum temperature and zonal wind velocity at 16.5 km have good coherency in the period of 10--25 days, which suggests that the structure of temperature around the tropopause is mainly controlled by Kelvin waves passing through. On the other hand, the minimum temperature fluctuation with a period of 25--50 days shows a large correlation with precipitable water vapor in the troposphere. ¿ 2000 American Geophysical Union