Vas-Cath (plaintiff) sued Mahurkar (defendant) for declaratory judgment of non-infringement and invalidity of two of Mahurkar’s United States patents, the ‘329 and ‘141 patents. Mahurkar counterclaimed that Vas-Cath infringed the patents. Mahurkar had filed a United States design patent application on March 8, 1982 that claimed a design for a catheter, but later abandoned the application on November 30, 1984. After the United States design application was filed but before abandonment, Mahurkar filed a Canadian design application with the same figures as the U.S. design application, the Canadian design issuing as a patent on August 9, 1982. Mahurkar filed utility applications in the United States for a catheter on October 1, 1984 and January 29, 1986, where these utility applications included the same figures as the abandoned U.S. design application and the issued Canadian design patent. These utility applications also claimed priority to the abandoned U.S. design application. The patent office noted, during the utility application prosecution, that these new patent application claims were fully supported by the disclosure in the abandoned design application. The utility applications eventually issued as the ‘329 and ‘141 patents. At trial, Vas-Cath argued that the design application did not sufficiently support the utility application so as to provide the earlier priority date. If the utility patents were not permitted to rely on the earlier design application filing date, then the Canadian design patent would become prior art against the later-filed U.S. utility patents. The district court agreed with Vas-Cath and held the utility patents anticipated. Mahurkar appealed.