John Cook, 20, of Upper Arlington, Ohio, was nine under par in eight matches as he won the Amateur Championship at the Plainfield Country Club, Plainfield, N.J. Cook defeated Scott Hoch, of Raleigh, N.C., 5 and 4, in the scheduled 36-hole final.

Among those he defeated were Doug Clarke, winner of the 1977 Southern Amateur and 1976 Trans-Miss Championships; Henri De Lozier, a semi-finalist and quarter-finalist in the 1975 and 1973 Amateurs, respectively; Kalua Makalena, the Hawaiian Open Champion; and, in a semi-final match, Michael Peck, the 1977 and 1978 Pacific 8 Champion.

Meanwhile, Hoch breezed through his half of the draw until his semi-final match with Bob Clampett, whose 1978 accomplishments included victories in the Porter Cup and Western Amateur, and low amateur in the Open. For the first time in Amateur history, both semi-final matches were decided in extra holes.

Cook and Peck played two under par golf for the first 18 holes. Cook settled the match with a birdie 3 on the second extra hole, a long par 4. Hoch and Clampett were playing even-par golf through the first 18 holes. Hoch won with a par 4, also at the 20th hole.

In the final, Cook jumped to a quick 2-up lead after two holes. Hoch stayed close, however, and was one down after the first nine holes, despite scoring 40 to Cook's 37. Cook responded with 32 on the second nine, including five birdies, and led 5 up at the lunch break.

Cook won the first three holes of the afternoon round with a par-birdie-birdie start to take an 8-up lead, the widest margin of the match. Hoch closed the gap slightly, but could come no closer than 5 down. Cook holed a four-foot par putt at the 32nd hole to win the Championship. In those 32 holes, there were 14 birdies-Cook had eight and Hoch six.

Two former Amateur Champions-Marvin Giles, III, (1972) and Fred Ridley (1975) -were entered. Giles lost in the second round, Ridley in the first round. Doug Fischesser, the runner-up in the 1977 Amateur, lost in the fifth round. Jay Sigel, a semi-finalist in the 1977 Amateur, lost in the fourth round. The field included four members of the 1977 U.S. Walker Cup Team-Ridley, Sigel, Vance Heafner, who lost in the third round, and Gary Hallberg, who lost his first match.