| POS | ATHLETE | COUNTRY | MARK | Reaction Time | 
|---|---|---|---|---|
| 1 | Jamaica Junior |  JAM | 39.74 Q WJL | 0.188 | 
| 2 | Trinidad and Tobago Junior |  TTO | 39.88 Q | 0.160 | 
| 3 | France Junior |  FRA | 40.11 | 0.208 | 
| 4 | South Africa Junior |  RSA | 40.32 SB | 0.187 | 
| 5 | Canada Junior |  CAN | 40.38 SB | 0.153 | 
| Czech Republic Junior |  CZE | DNF | 0.163 | |
| Saudi Arabia Junior |  KSA | DNF | 0.145 | 
| POS | ATHLETE | COUNTRY | MARK | Reaction Time | 
|---|---|---|---|---|
| 1 | United States Junior |  USA | 39.69 Q WJL | 0.157 | 
| 2 | Nigeria Junior |  NGR | 39.95 Q SB | 0.203 | 
| 3 | Thailand Junior |  THA | 40.00 q | 0.191 | 
| 4 | Poland Junior |  POL | 40.24 | 0.204 | 
| 5 | Belgium Junior |  BEL | 40.43 | 0.189 | 
| 6 | Bahamas Junior |  BAH | 40.58 SB | 0.161 | 
| Australia Junior |  AUS | DNF | 0.191 | 
| POS | ATHLETE | COUNTRY | MARK | Reaction Time | 
|---|---|---|---|---|
| 1 | Japan Junior |  JPN | 40.04 Q SB | 0.172 | 
| 2 | Germany Junior |  GER | 40.06 Q | 0.199 | 
| 3 | Great Britain & N.I. Junior |  GBR | 40.07 q | 0.143 | 
| 4 | Brazil Junior |  BRA | 40.56 SB | 0.176 | 
| 5 | Spain Junior |  ESP | 40.82 | 0.154 | 
| 6 | Zimbabwe Junior |  ZIM | 42.21 PB | 0.180 | 
| 7 | Bahrain Junior |  BRN | 42.93 PB | 0.213 |