Phelps, who finished second in the 400 metres individual medley on Monday and is the second fastest qualifier for Wednesday night's 200 freestyle final, cruised into the semi-finals of the 200 butterfly.
Conserving his energy, the 14-times Olympic gold medallist easily won his heat in one minute 57.75 seconds, more than seven seconds outside his world record, to qualify equal third fastest behind Bobby Bollier (1:56.69).
Franklin, who has the fastest time for Wednesday night's 100 backstroke final, also posted the third quickest time in the women's 200 freestyle heats, stopping the clock at 1:68.62.
Allison Schmitt, who won the 400 freestyle final on Wednesday, topped the time sheets when she won her heat in 1:58.02, just ahead of Dana Vollmer, who has already booked her ticket to London by winning the 100 butterfly.
Franklin, a 17-year-old from Colorado billed as the next big thing in American swimming, has entered five events at the trials but said she was having no problems with the exhausting schedule.
"Right now, I still feel awesome," she told reporters. "I feel full of energy."
Hoff, who made the Athens Olympics at age 15 and swam in six events at the 2008 Beijing Olympics but failed to win a gold medal in any of them, bombed out of the 200 freestyle when she finished 20th overall, missing the semis.
A day earlier, she finished 20th in the 400 freestyle and had pulled out of the 400 individual medly. She is still entered in the 800 freestyle but is suffering from a virus and is resigned to missing London.
"I felt better today, I was actually able to eat, but I just didn't have it," Hoff said. "But I don't want to make excuses."