units of the U.S. Seventh Fleet, and ranged the western Pacific from Japan to the Philippines. Returning to Pearl Harbor 1 July, Medregal resumed type and squadron operations between Hawaii and the West Coast. Between September 1961 and March 1962 she made a second deployment with the U.S. Seventh Fleet. In May 1962, Medregal and USS Carbonero, SS-337 participated in Operation Dominic I, Shot Frigate Bird near Christmas Island (now Kiribati). It was the first and only test of a fully operational Polaris missile with a 600 kt thermonuclear warhead, fired from USS Ethan Allan, SSBN-608. In October she steamed to the West Coast for ASW (SLAMEX) and Reserve training out of Puget Sound. She returned to Pearl Harbor in mid-December and for the next two years she maintained her pattern of operations between the Hawaiian Islands and the West Coast. Medregal departed Pearl Harbor for WestPac in mid-April 1965. Steaming first to Australia, she visited Brisbane, Sydney, and Melbourne, and participated in the commemoration of the Battle of the Coral Sea. Thence, in May she sailed to the Philippines for operations out of Subic Bay. On 13 July 1965 she was in a collision with a freighter while submerged in the South China Sea. Returned to Subic Bay for repairs. Extensive damage was done to the sail, all periscopes and snorkel system were completely inoperative. After patched up in Subic Bay, returned to Pearl Harbor for a short while then to Mare Island, Vellejo, Calif. for major repairs. Arrived back in Pearl Harbor late December 1965. Back in Pearl Harbor late in 1965, Medregal operated there until departure for Japan 2 July 1966. After reaching Yokosuka on 15 July, she joined Seventh Fleet aircraft carriers and destroyers for ASW operations in the western Pacific, and readiness and alert maneuvers with ships of the Republic of China Navy (based in Taiwan). During the rest of the year she continued to support peacekeeping operations in the troubled Far East. In January 1967, Medregal returned to her home port in Hawaii where she resumed her type training and squadron exercises with SubRon 1. She continued duty out of Pearl Harbor until 1 May when she was assigned to SubRon 3 out of San Diego, California. On 1 May 1967, Medregal was reclassified with hull classification symbol AGSS-480'''. On 6 February 1969 Medregal sank the as a target off the coast of California.