This paper examines the changes in trading activity around stock splits, and its impact on both the volatility and the bid-ask spread. After a stock split, there is a significant increase in the volatility and the spread, even after controlling for the effects of microstructure biases like price discreteness and bid-ask bounce. The change in the number of trades is positively related to the change in total volatility, as well as to the temporary and permanent components of volatility. This suggests that the change in trading activity is associated with both informed and noise traders. The change in the number of trades is also negatively related to the change in the total spread, as well as the adverse information content of the spread. Firms that are successful in attracting a large number of additional trades to their stock experience a smaller increase in spreads. These results suggest that a crucial determinant of the liquidity changes experienced by a firm after a stock split is the success of the split in attracting new trades to the security.