All unrealized capital gains are also taxed upon giving up citizenship. Furthermore, one still pays U.S. Estate taxes on what one has left upon death, <i>no matter how many years in the past one gave up his or her citizenship</i>. Currently, Federal estate tax is 40% (there is also state estate tax up to 20%).<p>You also are not allowed to spend too much time back in the US once you have relinquished citizenship without triggering US income taxes again.