Like Lord Flasheart, I'm not exactly sure what you mean? My guess is that you want to sell short, i.e. attempt to profit from stocks that you think will fall in value rather than rise in value. If this is the case, then most online brokers will allow you to do this in one form or another. In other words, you 'borrow' the stock from them to sell to a third party and then buy it back at a later date (at a lower price for a profit or a higher one for a loss) and then return the stock to your broker. This is all done automatically of course, you won't actually have to stand in line at your local post office with a a big parcel of shares to send back to your broker!