More than 10 million electronic bookings have now been made using Choose and Book, NHS Connecting for Health (CfH) has said.
One year ago, CfH reported that the programme had been used to book five million bookings.
Choose and Book's National Medical Director, Dr Stephen Miller. said: "I am very excited to have reached the 10th million electronic booking.
"It is significant because it gives a clear indication that Choose and Book is making good progress in becoming the NHS's everyday method of referral.
"My patients have responded very positively to Choose and Book, and I know that their endorsement has been replicated around the country."
The role of Choose and Book in the NHS is becoming well established, with more than 90% of GP practices having used the system over the past six weeks.
On average, CfH claims, around 50% of all outpatient referrals to see a specialist go through Choose and Book.
CfH also says that All NHS acute trusts are now using Choose and Book, along with 91% of all GP practices in England, which send over 105,000 referrals per week through the system.
Related story: Study finds patients not getting full Choose and Book benefits