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Studies of upward flashes from tall structures around the world have been reported since 1939. The characteristics of the triggering mechanism and of the upward flashes are of increasing interest to wind power turbines, telecommunication toware and power distribution companies. Observations of upward flashes in Brazil are recent. Since 2012, upward events were observed in all different seasons of year. They initiate on several towers in Sao Paulo, a city in southeast Brazil at an average elevation of around 800 meters above sea level and a flash density of 15 flashes/km².year. Some of the towers are located on top of buildings or hills. In this study, we will present some characteristics of these upward flashes, based on high speed video observation: flash duration, presence of subsequence of return stroke, previous lightning events, initial continuous current pulses and the presence recoil leader.