The 2005 split-share reform in China mandated the conversion of previously non-tradable shares into tradable status. The reform was swift and changed investors?ability to trade corporate equities in a US$400 billion market. This paper examines the e¤ects of the 2005 stock market reform on ?rms? real and ?nancial outcomes. It does so exploiting multiple institutional features of the conversion program. We ?rst examine a small pilot trial conducted at the beginning of the reform, which we are able to replicate using the same data and selection criteria that was used by regulators. We also take advantage of the staggered nature of the larger conversion schedule, whereby over a thousand ?rms converted their outstanding shares at di¤erent times within a pre-speci?ed window. These various wrinkles produce counterfactuals against which to gauge the economic e¤ects of secondary equity trading. Using a time-varying treatment estimation approach, we identify increases in corporate pro?tability, investment, value, and productivity as pre-existing shares were allowed to trade in or- ganized exchanges. We also identify changes in ?rms?propensity to issue new shares, pay dividends, and engage in merger deals. Our ?ndings provide new insights on the role of stock markets in shaping corporate behavior and on the impact of regulation on economic growth.