Antitrust Remedies Improvements Act of 1986

Antitrust Remedies Improvements Act of 1986 - (No title I).

Title II: Treble Damage Reform - Amends the Clayton Act to reduce the amount recoverable in a private antitrust action from treble to actual damages sustained, except when the damages are sustained by reason of the plaintiff being overcharged or underpaid by the liable party. Requires payment to the prevailing plaintiff in an actual damage case, or a treble damage case under specified circumstances, of interest on actual damages for the period beginning on the date of injury and ending on the date of judgment (prejudgment interest).

Entitles the United States to recover treble damages when it is injured by being overcharged or underpaid by an antitrust violation. Provides for the payment of prejudgment interest on the actual damages recovered by the United States in an antitrust action.

Provides for the payment of prejudgment interest on the total damage recovered in antitrust actions commenced by State attorneys general.

Title III: Defendants' Attorneys' Fees - Amends the Clayton Act to direct the court to award the cost of suit, including a reasonable attorney's fee, to a substantially prevailing defendant in a private antitrust action or a private action for injunctive relief against an antitrust violation if the court finds that the plaintiff's conduct was frivolous, unreasonable, without foundation, or in bad faith.

Title IV: Claim Reduction - Amends the Clayton Act to direct the court in an antitrust action to reduce the claim of any claimant who releases any person from liability by the greatest of: (1) a stipulated amount; (2) the consideration paid for release; or (3) the actual damages fairly allocable to the released person and interest thereon. Requires damages to be allocated on the basis of: (1) each competitor's proportionate share of the total competitors' overcharges or underpayments where the claim is based upon damages substained by reason of overcharges or underpayments resulting from a contract, combination, or conspiracy among competitors; or (2) each party's relative responsibility for the origination or perpetration of the antitrust violation, whichever method the court determines to be more equitable.

Title V: Effective Date - Applies this Act to actions commenced after its enactment.