No, you can't get a margin call for holding UPRO, the worst is that the value of the securities will drop to zero. I'll admit that leveraged ETFs such as UPRO have held up pretty well over the last decade, even through the pandemic crash. However, you'll notice that most leveraged ETFs aren't very old. The earliest seem to have been started in mid-2009. My understanding is thar during a prolonged bear market (ie. 2008, not the pandemic), that volatility decay will eat the value down to zero and the ETF will be delisted. Furthermore, the leveraged ETFs generally hold swaps and derivatives rather than the actual underlying securities, and these instruments seem to break during prolonged bear markets. If you are good at predicting bear markets, or if you use trailing stops, you might be able to make off like a bandit with UPRO. That said, if it were that easy, why isn't everyone doing it?