Whats the penalty for using steroids in MLB?

you will be beat up by Sammy Sosa wearing a banana suit

Here's the text from Attachment 18, Major League Baseball's Joint Drug Prevention And Treatment Program (ratified 2006) to the current Collective Bargaining Agreement (which covers the 2007-11 seasons).

Part 8(B):

Player Tests Positive for a Performance Enhancing Substance

1. First positive test result: a 50-game suspension;

2. Second positive test result: a 100-game suspension; and

3. Third positive test result: permanent suspension from Major League and Minor League Baseball; provided, however, that a Player so suspended may apply, no earlier than one year following the imposition of the suspension, to the Commissioner for discretionary reinstatement after a minimum period of two years. The Commissioner shall hear any such reinstatement application within 30 days of its filing and shall issue his determination within 30 days of the closing of the application hearing. A Player may challenge the Commissioner’s determination on such application under the Grievance Procedure set forth in Article XI and any such challenge may include a claim that a suspension beyond two years would not be for just cause; provided, however, that the Arbitration Panel shall have no authority to reduce any suspension imposed pursuant to this Section 8.B.3 to a period of less than two years.

Remember, "permanent" ≠ "lifetime". It is, however, a minimum of two years.

First positive test - 50 games

Second positive test - 100 games

Third positive test - lifetime suspension

These didn't go into place until only a couple of seasons ago, replacing penalties that were much lighter.

They bicker on and on about until about the time they give you a multiple-game suspension and turn you into a star for beating the system with the thanks of a grateful nation.

Cy youngs and the home run crown....