Antitrust Criminal Penalty Enhancement and Reform Act of 2003

Antitrust Criminal Penalty Enhancement and Reform Act of 2003 - Provides that in a civil action alleging a violation of the Sherman Act or of any similar State law based on conduct covered by an antitrust leniency agreement, the amount of damages recovered by a claimant from an applicant and cooperating individuals who satisfy this Act's requirements shall not exceed that portion of the actual damages sustained by the claimant that is attributable to the commerce done by the applicant in the goods or services affected by the violation (thus shielding organizations that cooperate with the Government from liability for treble damages).

Provides that an applicant or cooperating individual satisfies this Act's requirements if the court determines that such applicant or individual has provided satisfactory cooperation to the claimant, including: (1) providing a full account of all facts known that are potentially relevant to the civil action; and (2) furnishing all potentially relevant items that are in the applicant's or cooperating individual's possession or control.

Amends: (1) the Sherman Act to increase maximum prison sentences (from three years to ten years) and raise the maximum fine for individuals (from $350,000 to $1 million) for restraint of trade among the States, monopolizing trade, and other restraints of trade; and (2) the Antitrust Procedures and Penalties Act (Tunney Act) to require (current law allows) the court to consider specified factors, including the competitive impact of a judgment.