Eddie Gregory of Brooklyn executed the classic response to a southpaw tonight and stopped Marvin Johnson of Indianapolis in the 11th round for the World Boxing Association version of the light heavyweight championship.

Referee Carlos Berrocal of Panama halted the bout with 2 minutes 43 seconds gone of the round after Gregory raked Johnson with right leads and followed up with left hooks.

One right turned Johnson's legs to rubber. The referee paused to look at the bloody, weary Johnson and intervened.

Gregory leaped in the air in triumph almost before the crowd realized what was transpiring. As a mob of Stetson-hatted Gregory fans scrambled into the ring, the University of Tennessee band began playing "East Side, West Side," to salute the new champion from New York.

Gregory put Johnson down in the third round with a three-punch combination, but was unable to finish him and Johnson came back strong for a few rounds. It was the only knockdown of the fight.

All three officials had Gregory ahead through 10 rounds.

Berrocal scored the fight 97-93 for Gregory. Judge Luis Sulbaran of Venezuela had Gregory leading, 98-96. The second judge, Guillermo Bauza Romero of Mexico, had Gregory ahead, 99-98.

It was Gregory's 36th victory in 41 bouts and his 30th by a knockout. He has figured in one draw. In a previous try for the WBA title, he was decisioned by Victor Galindez of Argentina in 1977.

Johnson tired badly, and though only 25 years old, looked like a battered old man at the finish after Gregory bloodied his face. It was only his fourth loss in 28 bouts, in which he had won 24 and knocked out 18.

Gregory patiently pursued the approved strategy against a left-hander like Johnson, by shuffling to the left of Johnson and popping him with right leads. Gregory survived a bruised left eye he suffered in the fifth round, when his nose also was reddened. He is 27.

Johnson had moderate success in the middle rounds with right jabs to the nose but Gregory's celebrated counterpunching ability often made them costly. A body blow from Gregory doubled up the champ in the eighth and Johnson's white trunks were spotted with blood.

Gregory staggered Johnson with a solid right to the face with eight seconds left in the ninth round and brought blood from the champion's nose in the 10th. Gregory scored with a good right hand to the head early in the round and a solid shot to the body in the final seconds that semmed to take the stream out of Johnson.