| Final | time | | | 1. Valerie Brisco-Hooks |  States | 48.83s | OR | | 2. Chandra Cheeseborough | States | 49.05s | | | 3. Kathy Cook |  Britain | 49.43s | | | 4. Marita Payne |  Canada | 49.91s | | | 5. Lillie Leatherwood |  United States | 50.25s | | | 6. Ute Thimm |  West Germany | 50.37s | | | 7. Charmaine Crooks | Canada | 50.45s | | | 8. Ruth Waithera |  Kenya | 51.56s | |
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| | | Venue: Los Angeles Memorial Coliseum 100,000. -- competitors from -- nations. |
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| | | First 4 from each Semi advanced to Final. |
| Semi 1 | time | | | 1. Valerie Brisco-Hooks | United States | 51.14s | | | 2. Kathy Cook |  Great Britain | 51.49s | | | 3. Charmaine Crooks | Canada | 51.53s | | | 4. Ruth Waithera | Kenya | 52.21s | | | 5. June Griffith |  Guyana | 52.39s | | | 6. Cathy Rattray-Williams |  Jamaica | 53.23s | | | 7. Marie Mathieu |  Puerto Rico | 53.69s | | | -. Gaby Bußmann | West Germany | DNS | |
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| Semi 2 | time | | | 1. Chandra Cheeseborough | United States | 50.32s | | | 2. Lillie Leatherwood | United States | 50.83s | | | 3. Marita Payne | Canada | 50.94s | | | 4. Ute Thimm | West Germany | 51.03s | | | 5. Molly Killingbeck | Canada | 51.72s | | | 6. Michelle Scutt | Great Britain | 52.07s | | | 7. Ilrey Oliver | Jamaica | 52.14s | | | 8. Helen Barnett | Great Britain | 52.26s | |
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| Heat 1 | time | | | 1. Chandra Cheeseborough | United States | 50.94s | | | 2. Charmaine Crooks | Canada | 52.04s | | | 3. Ilrey Oliver | Jamaica | 52.19s | | | 4. June Griffith | Guyana | 52.27s | | | 5. Heike Schulte-Mattler | West Germany | 52.77s | | | 6. Erica Rossi |  Italy | 53.04s | | | 7. Jocelyn Joseph |  Antigua Barbuda | 53.63s | | | 8. Zonia Meigham |  Guatemala | 55.64s | |
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| Heat 2 | time | | | 1. Gaby Bußmann | West Germany | 52.42s | | | 2. Kathy Cook | Great Britain | 52.64s | | | 3. Molly Killingbeck | Canada | 52.77s | | | 4. Cathy Rattray-Williams | Jamaica | 52.78s | | | 5. Gail Emmanuel |  Trinidad Tobago | 54.07s | | | 6. Elanga Buala |  Papua New Guinea | 56.82s | | | 7. Mercy Addy |  Ghana | 58.91s | |
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| Heat3 | time | | | 1. Lillie Leatherwood | United States | 52.05s | | | 2. Marita Payne | Canada | 52.89s | | | 3. Helen Barnett | Great Britain | 52.94s | | | 4. Marie Mathieu | Puerto Rico | 53.27s | | | 5. Emma Tahapari |  Indonesia | 55.82s | | | 6. Reawadee Srithoa |  Thailand | 58.11s | |
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| Heat 4 | time | | | 1. Valerie Brisco-Hooks | United States | 51.42s | | | 2. Ruth Waithera | Kenya | 52.53s | | | 3. Ute Thimm | West Germany | 52.53s | | | 4. Michelle Scutt | Great Britain | 52.89s | | | 5. Cynthia Green | Jamaica | 53.61s | | | 6. Carlon Blackman |  Barbados | 54.26s | | | 7. Mina El-Jas Zeina |  Lebanon | 59.56s | |
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