We evaluate the enforcement of information barriers—China Walls—within conglomerates. Our setting is the 25 million trades in 2018–2024 in the Israeli Shekel market, where the SEC tightened the China Walls around dealers from July 2018. Our difference-in-differences design compares the trade volumes and profits of funds that are affiliated with, clients of, or entirely unrelated to a dealer around the days when the dealer is likely to hold valuable information. Before July 2018, dealers extensively share information with both their clients and affiliate funds, and price discovery is rapid. After July 2018: (i) dealers cease sharing information with their affiliate funds; (ii) they continue sharing with their clients unabated; (iii) price discovery slows; (iv) the trading costs paid by affiliate funds decline; and (v) the trading costs paid by other funds rise. A back-of-the-envelope calculation shows that the China Walls eliminated 90.1% of profits by the affiliate funds on event days.