The aims of this study are to examine how liquidity in the Government of Canada securities market has evolved over the 1990s and to determine what factors influence the level of liquidity in this market, with some comparisons to the U.S. Treasury securities market. We find empirical support for the hypothesis that an increase in effective supply of the securities enhances market liquidity. Empirical evidence also indicates that interest rate volatility tends to reduce market liquidity. The study finds that dealer concentration has either remained constant or has declined slightly from 1993 to 1998; that the share of interdealer trading carried out via interdealer brokers has increased significantly; and that non-resident trading has increased over the sample period. We argue that these changes would, in theory, enhance market liquidity. The study indicates a higher degree of market transparency in the U.S. Treasury securities market than in the Government of Canada securities market. The difference in transparency has likely engendered a significant difference in the level of market liquidity across countries. (Note that, since this study has been written, the CanPX transparency system has been introduced. This has had the effect of reducing the transparency discrepancy across the markets.)