British Paralympic champions Jessica-Jane Applegate, Bethany Firth and Ellie Simmonds all claimed world bests at the National Para-swimming Championships in Manchester.
Applegate, 19, beat her own mark in the S14 100m butterfly and also set a new time in the 100m freestyle.
However Firth got the better of Applegate in the S14 200m freestyle in a new world best.
Simmonds, 21, improved her own standard in the SM6 200m medley.
She managed a time of three minutes 0.01 seconds to beat the 3.01.02 she managed in winning world gold in Glasgow in July.
Firth, who missed the World Championships through injury, showed she is back to her best and well on track for Rio with a time of 2:04.44 - beating Russian world champion Valeriia Shabalina's 2:04.98 from July. Applegate was second in 2:05.88 - just short of her personal best.
Newcomer Rebecca Redfern set a new European best in the SB13 100m breaststroke.
The 16-year-old, who is visually impaired, finished in 1:18.99, beating the old mark of 1:19.55.
There was also a European best of 55.09 for Tom Hamer in the men's S14 100m freestyle, although it is not an event on the Rio Paralympic programme.
All of the times are subject to ratification by the International Paralympic Committee.