Connecting for Health has announced that 10 million "bookings" have been made through the Choose and Book system - a central part of the NHS's National Programme for IT.
This milestone comes 12 months after the programme reached the five million bookings milestone in August 2007.
The government's original plans were for GPs to be able to book every hospital appointment electronically by the end of 2005.
This has not proved possible, in part because not all GP systems can exchange Choose and Book data with hospital systems, and also because some doctors do not like using the technology which they regard as slow and cumbersome.
On average around 50 percent of all outpatient referrals to see a specialist go through Choose and Book.
Connecting for Health said: "As each day passes more and more patients are benefiting from Choose and Book."
It added: "Patients are now able to book their appointments electronically at a place, date and time convenient to them anywhere in the country."
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 their endorsement has been replicated around the country."
Connecting for Health says that Choose and Book is becoming "well established, with over 90 percent of GP practices having used the system over the past six weeks".
It is unclear how many of the 10 million "bookings" are actual hospital appointments. Sometimes the appointments are cancelled, or patients do not always confirm by phone appointments for which an electronic booking number has been issued.