GPs are still prescribing antibiotics unnecessarily for coughs and colds against national guidelines, UK research has suggested.
Antibiotics are commonly prescribed by GPs
Analysis of GP records showed they also were prescribed too commonly for sore throats and ear infections.
There is no evidence prescribing them prevents serious complications except for chest infections, the British Medical Journal reported.
Experts want to see less prescribing to prevent resistance developing.
Guidelines advise against their routine use in patients with upper respiratory tract infections, such as coughs, colds and sinusitis, as well as sore throats and ear infection because these illnesses tend to be caused by a virus.
Antibiotics are also not generally recommended for chest infections unless a patient has pneumonia.
The researchers from the UCL Centre for Infectious Disease Epidemiology in London found that between 1994 and 2000 rates of antibiotic prescribing for acute respiratory infections fell by 45% - in line with campaigns to cut their use.
But by 2000, two-thirds of patients with respiratory infections were still prescribed antibiotics.
Around 90% of those with chest infections were given the drugs, along with 80% of those with of ear infections and 60% of patients with sore throats.
The researchers said GPs may believe antibiotics could prevent serious complications from developing.
But analysis of the data showed such complications are rare after upper respiratory tract infection, sore throat and ear infection.
And antibiotics have little effect on reducing the risk further - in fact 4,000 courses would have to be prescribed to prevent one serious complication.
Mastoiditis - an infection of the mastoid bone of the skull, which sometimes occurs after ear infection
Quinsy- an abscess at the back of the throat that can sometimes follow a sore throat
Pneumonia - an infection of the lungs, which can occur after a chest infection
However, only 39 patients aged 65 and over would have to be treated with antibiotics for a chest infection to prevent a case of pneumonia.
For younger adults between 96 and 119 would have to receive antibiotics to prevent a case of pneumonia.
Study leader Dr Andrew Hayward said GPs are often criticised for prescribing antibiotics in patients with chest infection but that this strategy seems sensible, particularly in the elderly.
But he added: "It shows there's still clear scope for reductions in antibiotic prescribing for upper respiratory tract infections.
"From the point of view of prevention of severe illness they can be confident that the number of people they need to treat is really not worth it, especially as antibiotics are not without side effects and there are concerns over antibiotic resistance."
He said more research was needed to help doctors differentiate between chest infection and pneumonia.
Dr Dermot Ryan, a GP in Loughborough and clinical research fellow in primary care respiratory medicine at the University of Aberdeen, said the data on chest infections backed up previous research which had shown cuts in antibiotic use had driven up rates of pneumonia.
"With regards upper respiratory tract infections a lot of work in primary care is being unravelled by the government policy that the patient can get what they want when they want it.
"I've spoken to GPs who live in fear of complaints - they are stuck between a rock and a hard place."