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| August 16 (preliminaries and finals)|
The women's 100 metre butterfly competition of the swimming events at the 1991 Pan American Games took place on 16 August. The last Pan American Games champion was Janel Jorgensen of US.
This race consisted of two lengths of the pool, all in butterfly.
Swimming at the 1991 Pan American Games – Women's 100 metre butterfly Wikipedia
All times are in minutes and seconds.
The final was held on August 16.