| POS | BIB | ATHLETE | COUNTRY | MARK | Reaction Time | 
|---|---|---|---|---|---|
| 1 | 1481 | Michael Johnson |  USA | 43.95 Q | 0.143 | 
| 2 | 993 | Alejandro Manuel Cárdenas |  MEX | 44.37 Q NR | 0.128 | 
| 3 | 153 | Sanderlei Parrela |  BRA | 44.37 Q AR | 0.186 | 
| 4 | 533 | Mark Richardson |  GBR | 44.47 Q SB | 0.210 | 
| 5 | 1454 | Jerome Davis |  USA | 44.51 PB | 0.143 | 
| 6 | 1141 | Tomasz Czubak |  POL | 44.62 NR | 0.184 | 
| 7 | 862 | Kennedy Ochieng |  KEN | 45.57 | 0.312 | 
| 8 | 814 | Danny McFarlane |  JAM | 45.86 | 0.246 | 
| POS | BIB | ATHLETE | COUNTRY | MARK | Reaction Time | 
|---|---|---|---|---|---|
| 1 | 808 | Gregory Haughton |  JAM | 45.09 Q | 0.155 | 
| 2 | 516 | Jamie Baulch |  GBR | 45.24 Q | 0.162 | 
| 3 | 1293 | Matija Å estak |  SLO | 45.47 | 0.144 | 
| 4 | 1281 | Ibrahima Wade |  SEN | 45.66 | 0.242 | 
| 5 | 156 | Anderson Jorge dos Santos |  BRA | 45.67 | 0.174 | 
| 1498 | Antonio Pettigrew |  USA | DQ | 0.308 | |
| 1513 | Jerome Young |  USA | DQ | 0.163 | |
| 1160 | Piotr Rysiukiewicz |  POL | DNF | 0.224 |