Athletics at the 1955 Pan American Games – Men's 400 metres

Heats

Held on 17 March

Rank	Heat	Name	Nationality	Time	Notes
1	1	Lou Jones	United States	47.66	Q, GR
2	1	Mel Spence	Jamaica	47.86	Q
3	1	Evaristo Eddie	Venezuela	47.94	Q
4	1	Jorge Terán	Mexico	48.78
5	1	Ovidio de Jesús	Puerto Rico	49.97
1	2	Guillermo Gutiérrez	Venezuela	48.31	Q
2	2	Argemiro Roque	Brazil	48.62	Q
3	2	Allan Moore	Jamaica	48.83	Q
4	2	Pablo Salinas	Mexico	49.57
5	2	Cyril Johnson	Bahamas	51.62
	2	Angel García	Cuba	DNF
1	3	Jim Lea	United States	48.93	Q
2	3	Frank Rivera	Puerto Rico	48.94	Q
3	3	Dick Harding	Canada	49.27	Q
4	3	Evelio Planas	Cuba	49.47
1	4	Jesse Mashburn	United States	50.59	Q
2	4	Waldemiro Monteiro	Brazil	53.90	Q

Semifinals

Held on 17 March

Rank	Heat	Name	Nationality	Time	Notes
1	1	Lou Jones	United States	47.10	Q, GR
2	1	Jim Lea	United States	47.69	Q
3	1	Evaristo Eddie	Venezuela	47.91	Q
4	1	Allan Moore	Jamaica	48.34
5	1	Argemiro Roque	Brazil	48.55
1	2	Jesse Mashburn	United States	47.51	Q
2	2	Frank Rivera	Puerto Rico	48.01	Q
3	2	Mel Spence	Jamaica	48.09	Q
4	2	Dick Harding	Canada	48.28
5	2	Guillermo Gutiérrez	Venezuela	48.61
6	2	Waldemiro Monteiro	Brazil	49.66

Final

Held on 18 March

Rank	Name	Nationality	Time	Notes
	Lou Jones	United States	45.68	WR
	Jim Lea	United States	45.78
	Jesse Mashburn	United States	46.44
4	Frank Rivera	Puerto Rico	48.37
5	Mel Spence	Jamaica	48.84
	Evaristo Eddie	Venezuela	DNF