According to ABC television, a former congressional page aged 16 complained about e-mails he received from the six-term lawmaker.
The page forwarded some of Mr Foley's e-mails to a friend, with his own assessment: "Maybe it is just me being paranoid, but seriously. This freaked me out," he wrote.
"Sick sick sick sick sick."
"Did you have fun at your conference ... what do you want for your birthday coming up ... what stuff do you like to do," said some of the samples.
After ABC America released the messages, other pages, who are high-school-age aids, sent the broadcaster copies of e-mails from Mr Foley's account, Maf54.
Maf54: You in your boxers, too?
Teen: Nope, just got home. I had a college interview that went late.
Maf54: Well, strip down and get relaxed.
Another message read: Maf54: What ya wearing?
Teen: tshirt and shorts
Maf54: Love to slip them off of you.
And another said: Maf54: Do I make you a little horny?
Teen: A little.
Maf54: Cool.
Mr Foley has released a statement resigning immediately and apologising for his conduct.
“I am deeply sorry and I apologize for letting down my family and the people of Florida I have had the privilege to represent."
Mr Foley had co-chaired the House Caucus on Missing and Exploited Children, and recently introduced legislation to crack down on Internet child pornography sites.
He was favoured to win re-election against Democrat challenger Tim Mahoney on November 7, in legislative contests that could lose Republicans control either house of Congress.