| POS | ATHLETE | COUNTRY | MARK | Reaction Time | 
|---|---|---|---|---|
| 1 | Jamaica Junior |  JAM | 39.38 Q NJ | 0.170 | 
| 2 | Trinidad and Tobago Junior |  TTO | 39.50 Q NJ | 0.153 | 
| 3 | France Junior |  FRA | 39.93 q | 0.157 | 
| 4 | Italy Junior |  ITA | 40.16 q | 0.144 | 
| 5 | Australia Junior |  AUS | 40.51 PB | 0.143 | 
| 6 | Greece Junior |  GRE | 40.55 NJ | 0.170 | 
| Chile Junior |  CHI | DQ | 0.118 | |
| Bahamas Junior |  BAH | DNS | 0.000 | 
| POS | ATHLETE | COUNTRY | MARK | Reaction Time | 
|---|---|---|---|---|
| 1 | United States Junior |  USA | 39.18 Q WJL | 0.173 | 
| 2 | Brazil Junior |  BRA | 39.75 Q AJ | 0.129 | 
| 3 | Japan Junior |  JPN | 39.82 q | 0.128 | 
| 4 | Germany Junior |  GER | 39.85 q PB | 0.134 | 
| 5 | New Zealand Junior |  NZL | 40.35 PB | 0.162 | 
| 6 | Poland Junior |  POL | 40.59 | 0.160 | 
| 7 | Singapore U20 |  SGP | 41.87 NJ | 0.175 | 
| South Africa Junior |  RSA | DNS | 0.000 |