Using the introduction of margin trading in China, this study examines the effects of margin trading on the informativeness of trades and stock market liquidity. Using the methodology of Hasbrouck (1991 and 1993), I find that allowing investors to trade on margin leads to more informed trading. This increase in informed trading is mirrored by an increase in the adverse selection component of the bid-ask spread and a decrease in the relative weight placed on public information in trading decision. The discussed findings are more pronounced for stocks with relatively high levels of margin trading. Overall, the findings in the paper suggest that margin trading may lead to more information-based trading and lower levels of stock market liquidity.