NEW ADDITIONS!

Pokémon LV. X
* The Diamond & Pearl expansion introduces a new type of Pokémon-Pokémon LV. X! These cards represent the most powerful extremes that a Pokémon can reach, granting extra abilities, attacks, and more HP. They are played similarly to an Evolution card but have special rules as well.
* A Pokémon LV. X can't be played on a Pokémon that evolved that turn or on a LV. X already in play. (For example, if you evolved your Pokémon to Torterra this turn, you could not play Torterra LV. X on that Pokémon.)
* When a Pokémon LV. X is played, it keeps all cards attached to it as well as any damage counters it already had. It also keeps all attacks, Poké-Powers, and Poké-Bodies from the earlier level.
* When a Pokémon LV. X is played, it removes all Special Conditions and other effects from that Pokémon.
* A Pokémon LV. X shares the same name as the Pokémon it is put on top of. (For example, you can only have 4 Torterra in your deck-you could have 2 Torterra and 2 Torterra LV. X but not 4 of each.)
* A Pokémon LV. X is not considered an Evolution card. Cards that allow a player to search his or her deck for an Evolution card only (such as Professor Elm's Training Method) cannot be used to retrieve a Pokémon LV. X. If an effect removes the highest Stage Evolution card from a Pokémon LV. X, both the earlier evolution that the Pokémon LV. X is on top of and the Pokémon LV. X are removed.

Free Attack Costs
There are several Basic Pokémon in the game that have a special grayed-out circle instead of an attack cost. This means that the attack doesn't require any Energy to use it.

New Basic Energy Cards
Diamond & Pearl introduces two new basic Energy cards: Darkness and Metal. As with any basic Energy card, these cards are not restricted by the 4-per-deck rule. The basic Energy versions of Darkness and Metal Energy do not provide the additional benefits that the Special Energy versions do (i.e., additional damage for Darkness and reduced damage for Metal). Players may still use the Special Energy versions of Darkness and Metal Energy but are still restricted by the 4-per-deck rule for those cards.
If an effect allows you to search your deck for a basic Energy card, you may search your deck for the basic Energy version of Darkness (or Metal) Energy but not the Special Energy versions. If an effect allows you to search your deck for a Darkness (or Metal) Energy card, you may select either the basic Energy or Special Energy version.

New Term
Beginning with the Diamond & Pearl expansion, the term "Basic Pokémon or Evolution card" has been replaced with "Pokémon." When a card says to "Search your deck for a Pokémon…" it means that a player can select any Pokémon card, including Pokémon-ex and LV. X cards. If an older card uses the term "Basic Pokémon or Evolution card," treat it in all ways as though it used the term "Pokémon."

RULES CHANGES!

Beginning the game
The player who goes first now draws a card at the beginning of his or her turn. That player may not play ANY Trainer cards from his or her hand, during that first turn. (This includes playing Fossil cards to the Bench.)

Trainer Cards
Beginning with the Diamond & Pearl expansion, Stadium cards and Supporter cards now have their own card type and are no longer considered Trainer cards. The Stadium and Supporter cards have had their card faces updated to reflect this change.
Older cards that affect Trainer cards will affect any pre-Diamond & Pearl Trainer card, as well as any Diamond & Pearl Trainer, Stadium, or Supporter card. For example, if an older card says, "Search your deck for a Trainer card and put it into your hand," you may search your deck for any older Trainer card (including Stadium and Supporter cards) or any Diamond & Pearl Trainer, Stadium, or Supporter card, and put it in your hand.
Diamond & Pearl cards that affect Trainer cards will not affect any older Supporter or Stadium card, nor will it affect any Diamond & Pearl Stadium or Supporter card. For example, if a Diamond & Pearl card says, "Search your deck for a Trainer card and put it into your hand," you may not search for an older Supporter or Stadium or a Diamond & Pearl Supporter or Stadium card. Pokémon Tool and Technical Machine cards are still classified as Trainer cards.

Fossil Cards
Beginning with the Diamond & Pearl expansion, when a Fossil card is Knocked Out, it is treated as a Pokémon that has been Knocked Out, so a Prize card is drawn. If a Fossil card is discarded from play rather than Knocked Out, no Prize card is drawn.

Unown Pokémon
Beginning with the Diamond & Pearl expansion, Unown cards use Unown A, Unown B, etc., as Pokémon names, allowing players to use up to 4 of each in a deck. Older Unown cards are unaffected by this change, so those cards are still restricted by the 4-per-deck rule, regardless of which version of Unown they are. (For example, a player's deck may contain 4 older Unown, 4 Unown A, and 4 Unown B.) If a card refers to "an Unown card," it refers to any Unown, regardless of name.

Weakness and Resistance
The Weakness and Resistance calculations have been modified in Diamond & Pearl. All Pokémon now have a modifier next to their Weakness and Resistance (if any), which may increase or decrease the damage done to that Pokémon. Cards printed prior to Diamond & Pearl will continue to use the old calculations when determining damage (x2 damage for Weakness and -30 damage for Resistance).

TOURNAMENT LEGALITY!

Due to varying release schedules, the Pokémon Trading Card Game: Diamond & Pearl expansion will not be available in all markets at the same time. These schedules are varied due to translation time for both the video game and the trading card game, and the concurrent release of both products allows players in each market to enjoy the Diamond & Pearl experience in its entirety. The Modified format will be adjusted on a market-by-market basis to compensate for this variance. Additionally, the rules changes instituted in the Diamond & Pearl set will not affect game play in a market until Diamond & Pearl has been released in that market. Diamond & Pearl will be tournament-legal for the following major events during this tournament season:
* 2007 Battle Roads in North America
* 2007 Canadian National Championships
* 2007 U.S. National Championships
* 2007 Pokémon TCG World Championships: Last Chance Qualifier
* 2007 Pokémon TCG World Championships
Due to the close proximity of the Diamond & Pearl release to the Mexico National Championships, Diamond & Pearl will not be tournament-legal at that event. Additionally, the rules changes outlined above will not affect game play at the Mexico National Championships.
Pokémon Organized Play is working to ensure that players in the 2007 Pokémon TCG World Championships, as well as those in the Last Chance Qualifier, are able to maintain their competitive edge regardless of whether or not Diamond & Pearl has been released in their markets. Look for more information at www.op.pokemon-tcg.com in the near future.

Above info is from the Pokemon Organized Play site.