This excerpt taken from the TGT DEF 14A filed Apr 10, 2006.
Stock Options. Stock options were granted at the market value of the underlying Common Stock on the date of grant and have a 10-year term. The options are generally exercisable 25% after the first year, with an additional 25% exercisable after each of the next three years. To encourage continued service and to assist with orderly succession planning, option holders can qualify for an extended post-termination exercise period of up to five years (but not to exceed the ten-year term of the option) if they have at least 15 years of service and comply with specified advance notice of resignation requirements.