This paper studies gaming efficiency with data envelopment analyses (DEA) and its determinants with seemingly unrelated regressions (SUR). We show that gaming efficiency is higher in Macao than in Las Vegas and can be improved in both places. We find that Macao casino performance hinges on China's economic growth and visitor arrivals as well as VIP service and promotional marketing while non-gaming business and slot gaming are contributors to Las Vegas tourism efficiency. We also indicate that the 2008 global financial crisis and the 2014 China anti-corruption movement are hugely disruptive to gaming efficiency both in Macao and Las Vegas. Those results provide policy makers and casino managers with useful implications for efficiency enhancement in gaming-led tourism and hospitality.