The England defender is out of contract at the end of the season and, with the player seemingly intent on leaving, the Trotters are looking to cash in on one of their most prized players when the transfer window opens next month.
Chelsea boss Andre Villas-Boas made his interest in the 26-year-old public earlier this week with Cahill set to offer, at the very least, much-needed depth at centre-half after the Blues accepted a transfer request from Alex earlier this month.
And Villas-Boas' interest has apparently moved a step forward in the past few days after Bolton revealed today that negotiations had begun.
"Regarding Gary Cahill, there has been dialogue between ourselves and Chelsea. He is a top player and is fully focused on Bolton," a brief statement on their Twitter page read.