Appealed from: U.S. District Court for the Northern District of Georgia Senior Judge William C. O'Kelley Bayer brought two separate actions in the United States District Court for the Northern District of Georgia asserting that Elan Pharmaceuticals Research Corp. (Elan) infringed U.S. Patent No. 5,264,446 (the `446 patent). The first action asserted that Elan infringed by filing an abbreviated new drug application (ANDA) with the Food and Drug Administration (FDA) seeking approval of a 60 mg generic version of the invention claimed in the `446 patent. The second action asserted infringement in Elan's marketing of a commercial 30 mg generic version. On summary judgment, the district court collaterally estopped Bayer from pursuing either action based on the court's previous finding of non-infringement in a related 30 mg ANDA infringement case. Because the district court erred in finding that it had necessarily and sufficiently construed the claims of the `446 patent in the 30 mg ANDA infringement case, this court vacates and remands both cases. I.