What effects will the terrorist attack have on Wall Street and trading in general in the long term? First of all I think that interest of general population for stocks and stock market in general will substantionally decrease as people will realize how vulnerable and easy to disrupt our economy really is. There will be less liquidity, but on the other hand volatility may even increase. If there is a prolonged conflict with Afganistan and other similar countries (it is very likely scenario), overnight and long term holding of positions will be definitely less appealing for most traders. On the other hand, more people will be inclined for making short term profits as opposed to long term investing, so speculation and trading may get to the new level. Wall Street and Manhattan will start to lose their appeal as more people will realize how dangerous it is to have as centralized financial system as we do now. Markets will become decentralized more redundant and much harder to disrupt.