Patients who qualify will be able to save an estimated £100 a year
Up to 150,000 cancer patients in England can now start applying for free prescriptions on the NHS.
Gordon Brown announced in September he was abolishing charges for the treatment of cancer and its effects from 1 April.
Patients can apply for five-year exemption certificates entitling them to all their NHS prescriptions free of charge, not just those for cancer.
Application forms can be collected from GP surgeries and hospital clinics.
Applications received by 24 March will be processed in time for the start of the scheme on 1 April.
Patients who do not receive their certificate in time may have any prescription charges they have paid since 1 April refunded.
It is estimated that patients who qualify will be able to save up to £100 a year in prescription charges.
Campaigners have been calling for everyone with long-term conditions in England to be exempt from prescription charges, as they have already been scrapped in Wales and are being phased out in Scotland.
Northern Ireland has already reduced charges and is planning to phase them out for all patients by 2010.
The standard prescription charge is £7.10 per item.
Public Health Minister Dawn Primarolo said: "This new scheme gives people living with cancer one less worry at such a difficult time.
"I would urge patients to make an appointment with their GP from this week to talk about applying for their exemption certificate."
Ciaran Devane, chief executive of Macmillan Cancer Support, said: "We are delighted the government has listened and abolished prescription charges for cancer patients.
"This was absolutely the right thing to do. Cancer not only threatens your life, but can also make you poor.
"Free prescriptions will transform the lives of thousands of people living with cancer who were struggling to pay for drugs."
Michael Summers, vice-chairman of the Patients Association, said: "This is a welcome move, but we mustn't forget that not every cancer drug that patients want will be approved by NICE or that some primary care trusts will not allow them to be dispensed."
The Department of Health says the scheme will be extended to include all patients with long-term conditions at a later date.
This would make an estimated five million people exempt from charges.
A review of how to bring this measure in is being led by Professor Ian Gilmore, president of the Royal College of Physicians.