This paper examines the impact on the liquidity of NYSE/AMEX listed stocks when they were subsequently listed on the London or the Tokyo Stock Exchanges. It can be argued that the increased competition from foreign market makers will reduce the monopoly rents that specialists can earn, thereby improving their quotes. We find, however, that spreads do not decrease following a dual listing, though the depth of the quotes increases as predicted. The apparent increase in depth disappears once we account for changes in price, volume and return variance. We also find that the level of informed trading increases, which increases the cost to the specialist of providing liquidity, and explains why spreads do not decline in spite of increased competition. Consistent with an increase in informed trading, we also document an increase in trading activity.