The medical advice line - which people can call for help when their GP surgery is closed - has changed its number to 111.
While people have had to pay for calls to the advice service until now, the new number is free to call from both landline and mobile phones.
Health Secretary Alex Neil welcomed the change, saying: "I strongly believe that our NHS should be free at the point of care for all and this new number will help to protect these founding principles of the NHS."
A total of 1.5 million calls a year are made to NHS 24, with the service receiving up to 8,000 calls a day during its busiest times.
Previously, callers to NHS 24 who were phoning from a BT landline had been charged for a local rate call, but costs from other phone providers and mobiles could be more expensive.
Mr Neil said: "The new number is easy to remember and free to call, which will ensure everyone across Scotland can access support and advice from NHS 24 whenever they need it.
"NHS 24 already provides a valuable service to patients across Scotland when their GP surgery is closed and there will be absolutely no change to the high-quality service provided through this new number.
"By introducing the 111 number we are removing any barrier for the public to access the health advice out of hours.
"This will help to ensure people have access to health information and support, including access to a GP, when they really need it."
The Health Secretary also pledged that "in Scotland, the 111 number will be run by NHS 24 as a public service, in public hands - serving the needs of patients".
He added: "This is in complete contrast to the approach adopted by the NHS in England, where different organisations, including private-sector providers, are contracted to provide the number in different regions."
The introduction of the freephone number was welcomed by Lee Armstrong from Edinburgh, whose daughter Charlotte, seven, suffers from diabetes.
The mother-of-two said: "As a parent, I have always found it useful to have someone at the end of the telephone when GP surgeries are not open at the weekend or in the evenings.
"I think the move to the free telephone number will make it even easier for parents like me to contact the service in what is a positive development ."
Doctors leaders also welcomed the change, with Dr Andrew Buist, deputy chairman of the British Medical Association's Scottish General Practitioners Committee, stating: "Creating a new freephone number for NHS 24 will remove barriers to accessing this important part of our out-of-hours service. Patients will no longer have to worry about the cost of a phone call when seeking urgent health advice."
NHS 24 chief executive John Turner said: "By dialling 111, patients throughout Scotland will receive the same high quality, trusted service that NHS 24 has delivered for more than ten years.
"We will continue to work with our partners across Scotland to provide high-quality support to patients and their families on the new number, which is easy to remember and free to call.
"NHS 24 has been serving the people of Scotland for more than ten years now and the move to a freephone number represents the next stage in the development of the country's provider of telehealth and telecare services."
People will continue to be able to call NHS 24 on the old number - 08454 24 24 24 - for a limited time.